Re: Re: [External] Re: vmscan: Reclaim unevictable pages

Re: Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

[ cc linux-mm ]


From: Pankaj Suryawanshi
Sent: 14 March 2019 19:14:40
To: Kirill Tkhai; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



Hello ,

Please ignore the curly braces, they are just for debugging.

Below is the updated patch.


diff --git a/mm/vmscan.c b/mm/vmscan.c
index be56e2e..12ac353 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                sc->nr_scanned++;

                if (unlikely(!page_evictable(page)))
-                       goto activate_locked;
+                      goto cull_mlocked;

                if (!sc->may_unmap && page_mapped(page))
                        goto keep_locked;
@@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                } else
                        list_add(&page->lru, &free_pages);
                continue;
-
+cull_mlocked:
+                if (PageSwapCache(page))
+                        try_to_free_swap(page);
+                unlock_page(page);
+                list_add(&page->lru, &ret_pages);
+                continue;
 activate_locked:
                /* Not a candidate for swapping, so reclaim swap space. */
                if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||



Regards,
Pankaj


From: Kirill Tkhai <ktkhai@virtuozzo.com>
Sent: 14 March 2019 14:55:34
To: Pankaj Suryawanshi; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages


On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>
> I am using kernel version 4.14.65 (on Android pie [ARM]).
>
> No additional patches applied on top of vanilla.(Core MM).
>
> If  I change in the vmscan.c as below patch, it will work.

Sorry, but 4.14.65 does not have braces around trylock_page(),
like in your patch below.

See    https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65

[...]

>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index be56e2e..2e51edc 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                  page = lru_to_page(page_list);
>>                  list_del(&page->lru);
>>
>>                 if (!trylock_page(page)) {
>>                          goto keep;
>>                 }

************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are intended solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and please delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage caused by any virus transmitted by this email. *************************************************************************************************************************************************************

Re: Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

[ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]

From: Pankaj Suryawanshi
Sent: 15 March 2019 11:35:05
To: Kirill Tkhai; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



[ cc linux-mm ]


From: Pankaj Suryawanshi
Sent: 14 March 2019 19:14:40
To: Kirill Tkhai; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



Hello ,

Please ignore the curly braces, they are just for debugging.

Below is the updated patch.


diff --git a/mm/vmscan.c b/mm/vmscan.c
index be56e2e..12ac353 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                sc->nr_scanned++;

                if (unlikely(!page_evictable(page)))
-                       goto activate_locked;
+                      goto cull_mlocked;

                if (!sc->may_unmap && page_mapped(page))
                        goto keep_locked;
@@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                } else
                        list_add(&page->lru, &free_pages);
                continue;
-
+cull_mlocked:
+                if (PageSwapCache(page))
+                        try_to_free_swap(page);
+                unlock_page(page);
+                list_add(&page->lru, &ret_pages);
+                continue;
 activate_locked:
                /* Not a candidate for swapping, so reclaim swap space. */
                if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||



Regards,
Pankaj


From: Kirill Tkhai <ktkhai@virtuozzo.com>
Sent: 14 March 2019 14:55:34
To: Pankaj Suryawanshi; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages


On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>
> I am using kernel version 4.14.65 (on Android pie [ARM]).
>
> No additional patches applied on top of vanilla.(Core MM).
>
> If  I change in the vmscan.c as below patch, it will work.

Sorry, but 4.14.65 does not have braces around trylock_page(),
like in your patch below.

See     https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65

[...]

>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index be56e2e..2e51edc 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                  page = lru_to_page(page_list);
>>                  list_del(&page->lru);
>>
>>                 if (!trylock_page(page)) {
>>                          goto keep;
>>                 }

************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are intended solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and please delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage caused by any virus transmitted by this email. *************************************************************************************************************************************************************

Re: Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

It fixes the below issue.

1. Large size buffer allocation using cma_alloc successful with unevictable pages.

cma_alloc of current kernel will fail due to unevictable pages.

Solved the below issue of cma_alloc

-----------------------------------------------------------------------------------------------------------------------------------------
 [   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
 [   24.726949] page->mem_cgroup:bd008c00
 [   24.730693] ------------[ cut here ]------------
 [   24.735304] kernel BUG at mm/vmscan.c:1350!
 [   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
-----------------------------------------------------------------------------------------------------------------------------------------


From: Pankaj Suryawanshi
Sent: 15 March 2019 15:41:57
To: Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com; vbabka@suse.cz
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



[ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]

From: Pankaj Suryawanshi
Sent: 15 March 2019 11:35:05
To: Kirill Tkhai; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



[ cc linux-mm ]


From: Pankaj Suryawanshi
Sent: 14 March 2019 19:14:40
To: Kirill Tkhai; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



Hello ,

Please ignore the curly braces, they are just for debugging.

Below is the updated patch.


diff --git a/mm/vmscan.c b/mm/vmscan.c
index be56e2e..12ac353 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                sc->nr_scanned++;

                if (unlikely(!page_evictable(page)))
-                       goto activate_locked;
+                      goto cull_mlocked;

                if (!sc->may_unmap && page_mapped(page))
                        goto keep_locked;
@@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                } else
                        list_add(&page->lru, &free_pages);
                continue;
-
+cull_mlocked:
+                if (PageSwapCache(page))
+                        try_to_free_swap(page);
+                unlock_page(page);
+                list_add(&page->lru, &ret_pages);
+                continue;
 activate_locked:
                /* Not a candidate for swapping, so reclaim swap space. */
                if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||



Regards,
Pankaj


From: Kirill Tkhai <ktkhai@virtuozzo.com>
Sent: 14 March 2019 14:55:34
To: Pankaj Suryawanshi; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages


On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>
> I am using kernel version 4.14.65 (on Android pie [ARM]).
>
> No additional patches applied on top of vanilla.(Core MM).
>
> If  I change in the vmscan.c as below patch, it will work.

Sorry, but 4.14.65 does not have braces around trylock_page(),
like in your patch below.

See      https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65

[...]

>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index be56e2e..2e51edc 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                  page = lru_to_page(page_list);
>>                  list_del(&page->lru);
>>
>>                 if (!trylock_page(page)) {
>>                          goto keep;
>>                 }

************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are intended solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and please delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage caused by any virus transmitted by this email. *************************************************************************************************************************************************************

Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

Hello

shrink_page_list() returns , number of pages reclaimed, when pages is unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),page);

We can add the unevictable pages in reclaim list in shrink_page_list(), return total number of reclaim pages including unevictable pages, let the caller handle unevictable pages.

I think the problem is shrink_page_list is awkard. If page is unevictable it goto activate_locked->keep_locked->keep lables, keep lable list_add the unevictable pages and throw the VM_BUG instead of passing it to caller while it relies on caller for non-reclaimed-non-unevictable page's putback.
I think we can make it consistent so that shrink_page_list could return non-reclaimed pages via page_list and caller can handle it. As an advance, it could try to migrate mlocked pages without retrial.


Below is the issue of CMA_ALLOC of large size buffer : (Kernel version - 4.14.65 (On Android pie [ARM])).

[   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
[   24.726949] page->mem_cgroup:bd008c00
[   24.730693] ------------[ cut here ]------------
[   24.735304] kernel BUG at mm/vmscan.c:1350!
[   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM


Below is the patch which solved this issue :

diff --git a/mm/vmscan.c b/mm/vmscan.c
index be56e2e..12ac353 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                sc->nr_scanned++;

                if (unlikely(!page_evictable(page)))
-                       goto activate_locked;
+                      goto cull_mlocked;

                if (!sc->may_unmap && page_mapped(page))
                        goto keep_locked;
@@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                } else
                        list_add(&page->lru, &free_pages);
                continue;
-
+cull_mlocked:
+                if (PageSwapCache(page))
+                        try_to_free_swap(page);
+                unlock_page(page);
+                list_add(&page->lru, &ret_pages);
+                continue;
 activate_locked:
                /* Not a candidate for swapping, so reclaim swap space. */
                if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||




It fixes the below issue.

1. Large size buffer allocation using cma_alloc successful with unevictable pages.

cma_alloc of current kernel will fail due to unevictable page

Please let me know if anything i am missing.

Regards,
Pankaj



From: Pankaj Suryawanshi
Sent: 18 March 2019 13:15:22
To: Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; vbabka@suse.cz
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



It fixes the below issue.

1. Large size buffer allocation using cma_alloc successful with unevictable pages.

cma_alloc of current kernel will fail due to unevictable pages.

Solved the below issue of cma_alloc

-----------------------------------------------------------------------------------------------------------------------------------------
 [   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
 [   24.726949] page->mem_cgroup:bd008c00
 [   24.730693] ------------[ cut here ]------------
 [   24.735304] kernel BUG at mm/vmscan.c:1350!
 [   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
-----------------------------------------------------------------------------------------------------------------------------------------


From: Pankaj Suryawanshi
Sent: 15 March 2019 15:41:57
To: Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com; vbabka@suse.cz
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



[ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]

From: Pankaj Suryawanshi
Sent: 15 March 2019 11:35:05
To: Kirill Tkhai; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



[ cc linux-mm ]


From: Pankaj Suryawanshi
Sent: 14 March 2019 19:14:40
To: Kirill Tkhai; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages



Hello ,

Please ignore the curly braces, they are just for debugging.

Below is the updated patch.


diff --git a/mm/vmscan.c b/mm/vmscan.c
index be56e2e..12ac353 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                sc->nr_scanned++;

                if (unlikely(!page_evictable(page)))
-                       goto activate_locked;
+                      goto cull_mlocked;

                if (!sc->may_unmap && page_mapped(page))
                        goto keep_locked;
@@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                } else
                        list_add(&page->lru, &free_pages);
                continue;
-
+cull_mlocked:
+                if (PageSwapCache(page))
+                        try_to_free_swap(page);
+                unlock_page(page);
+                list_add(&page->lru, &ret_pages);
+                continue;
 activate_locked:
                /* Not a candidate for swapping, so reclaim swap space. */
                if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||



Regards,
Pankaj


From: Kirill Tkhai <ktkhai@virtuozzo.com>
Sent: 14 March 2019 14:55:34
To: Pankaj Suryawanshi; Michal Hocko
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages


On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>
> I am using kernel version 4.14.65 (on Android pie [ARM]).
>
> No additional patches applied on top of vanilla.(Core MM).
>
> If  I change in the vmscan.c as below patch, it will work.

Sorry, but 4.14.65 does not have braces around trylock_page(),
like in your patch below.

See       https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65

[...]

>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index be56e2e..2e51edc 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                  page = lru_to_page(page_list);
>>                  list_del(&page->lru);
>>
>>                 if (!trylock_page(page)) {
>>                          goto keep;
>>                 }

************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are intended solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and please delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage caused by any virus transmitted by this email. *************************************************************************************************************************************************************

Re: [External] Re: vmscan: Reclaim unevictable pages

[Vlastimil Babka]

On 3/15/19 11:11 AM, Pankaj Suryawanshi wrote:
> 
> [ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]

Can you send a proper patch with changelog explaining the change? I
don't know the context of this thread.

> From: Pankaj Suryawanshi
> Sent: 15 March 2019 11:35:05
> To: Kirill Tkhai; Michal Hocko
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
> 
> 
> 
> [ cc linux-mm ]
> 
> 
> From: Pankaj Suryawanshi
> Sent: 14 March 2019 19:14:40
> To: Kirill Tkhai; Michal Hocko
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
> 
> 
> 
> Hello ,
> 
> Please ignore the curly braces, they are just for debugging.
> 
> Below is the updated patch.
> 
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index be56e2e..12ac353 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>                 sc->nr_scanned++;
> 
>                 if (unlikely(!page_evictable(page)))
> -                       goto activate_locked;
> +                      goto cull_mlocked;
> 
>                 if (!sc->may_unmap && page_mapped(page))
>                         goto keep_locked;
> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>                 } else
>                         list_add(&page->lru, &free_pages);
>                 continue;
> -
> +cull_mlocked:
> +                if (PageSwapCache(page))
> +                        try_to_free_swap(page);
> +                unlock_page(page);
> +                list_add(&page->lru, &ret_pages);
> +                continue;
>  activate_locked:
>                 /* Not a candidate for swapping, so reclaim swap space. */
>                 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
> 
> 
> 
> Regards,
> Pankaj
> 
> 
> From: Kirill Tkhai <ktkhai@virtuozzo.com>
> Sent: 14 March 2019 14:55:34
> To: Pankaj Suryawanshi; Michal Hocko
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
> 
> 
> On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>>
>> I am using kernel version 4.14.65 (on Android pie [ARM]).
>>
>> No additional patches applied on top of vanilla.(Core MM).
>>
>> If  I change in the vmscan.c as below patch, it will work.
> 
> Sorry, but 4.14.65 does not have braces around trylock_page(),
> like in your patch below.
> 
> See     https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65
> 
> [...]
> 
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index be56e2e..2e51edc 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                  page = lru_to_page(page_list);
>>>                  list_del(&page->lru);
>>>
>>>                 if (!trylock_page(page)) {
>>>                          goto keep;
>>>                 }
> 
> ************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are intended solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and please delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage caused by any virus transmitted by this email. *************************************************************************************************************************************************************
> 

Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

Hello

shrink_page_list() returns , number of pages reclaimed, when pages is unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),page);

We can add the unevictable pages in reclaim list in shrink_page_list(), return total number of reclaim pages including unevictable pages, let the caller handle unevictable pages.

I think the problem is shrink_page_list is awkard. If page is unevictable it goto activate_locked->keep_locked->keep lables, keep lable list_add the unevictable pages and throw the VM_BUG instead of passing it to caller while it relies on caller for non-reclaimed-non-unevictable  page's putback.
I think we can make it consistent so that shrink_page_list could return non-reclaimed pages via page_list and caller can handle it. As an advance, it could try to migrate mlocked pages without retrial.


Below is the issue of CMA_ALLOC of large size buffer : (Kernel version - 4.14.65 (On Android pie [ARM])).

[   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
[   24.726949] page->mem_cgroup:bd008c00
[   24.730693] ------------[ cut here ]------------
[   24.735304] kernel BUG at mm/vmscan.c:1350!
[   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM


Below is the patch which solved this issue :

diff --git a/mm/vmscan.c b/mm/vmscan.c
index be56e2e..12ac353 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                sc->nr_scanned++;
 
                if (unlikely(!page_evictable(page)))
-                       goto activate_locked;
+                      goto cull_mlocked;
 
                if (!sc->may_unmap && page_mapped(page))
                        goto keep_locked;
@@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                } else
                        list_add(&page->lru, &free_pages);
                continue;
-
+cull_mlocked:
+                if (PageSwapCache(page))
+                        try_to_free_swap(page);
+                unlock_page(page);
+                list_add(&page->lru, &ret_pages);
+                continue;
 activate_locked:
                /* Not a candidate for swapping, so reclaim swap space. */
                if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||




It fixes the below issue.

1. Large size buffer allocation using cma_alloc successful with unevictable pages.

cma_alloc of current kernel will fail due to unevictable page

Please let me know if anything i am missing.

Regards,
Pankaj
  
From: Vlastimil Babka <vbabka@suse.cz>
Sent: 18 March 2019 14:12:50
To: Pankaj Suryawanshi; Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
  

On 3/15/19 11:11 AM, Pankaj Suryawanshi wrote:
> 
> [ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]

Can you send a proper patch with changelog explaining the change? I
don't know the context of this thread.

> From: Pankaj Suryawanshi
> Sent: 15 March 2019 11:35:05
> To: Kirill Tkhai; Michal Hocko
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
> 
> 
> 
> [ cc linux-mm ]
> 
> 
> From: Pankaj Suryawanshi
> Sent: 14 March 2019 19:14:40
> To: Kirill Tkhai; Michal Hocko
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
> 
> 
> 
> Hello ,
> 
> Please ignore the curly braces, they are just for debugging.
> 
> Below is the updated patch.
> 
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index be56e2e..12ac353 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>                 sc->nr_scanned++;
> 
>                 if (unlikely(!page_evictable(page)))
> -                       goto activate_locked;
> +                      goto cull_mlocked;
> 
>                 if (!sc->may_unmap && page_mapped(page))
>                         goto keep_locked;
> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>                 } else
>                         list_add(&page->lru, &free_pages);
>                 continue;
> -
> +cull_mlocked:
> +                if (PageSwapCache(page))
> +                        try_to_free_swap(page);
> +                unlock_page(page);
> +                list_add(&page->lru, &ret_pages);
> +                continue;
>  activate_locked:
>                 /* Not a candidate for swapping, so reclaim swap space. */
>                 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
> 
> 
> 
> Regards,
> Pankaj
> 
> 
> From: Kirill Tkhai <ktkhai@virtuozzo.com>
> Sent: 14 March 2019 14:55:34
> To: Pankaj Suryawanshi; Michal Hocko
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
> 
> 
> On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>>
>> I am using kernel version 4.14.65 (on Android pie [ARM]).
>>
>> No additional patches applied on top of vanilla.(Core MM).
>>
>> If  I change in the vmscan.c as below patch, it will work.
> 
> Sorry, but 4.14.65 does not have braces around trylock_page(),
> like in your patch below.
> 
> See      https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65
> 
> [...]
> 
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index be56e2e..2e51edc 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                  page = lru_to_page(page_list);
>>>                  list_del(&page->lru);
>>>
>>>                 if (!trylock_page(page)) {
>>>                          goto keep;
>>>                 }
> 
> ************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are intended  solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you  are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and please  delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage caused  by any virus transmitted by this email. *************************************************************************************************************************************************************
> 

    

Re: [External] Re: vmscan: Reclaim unevictable pages

[Kirill Tkhai]

Hi, Pankaj,

On 18.03.2019 12:09, Pankaj Suryawanshi wrote:
> 
> Hello
> 
> shrink_page_list() returns , number of pages reclaimed, when pages is unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),page);

the general idea is shrink_page_list() can't iterate PageUnevictable() pages.
PageUnevictable() pages are never being added to lists, which shrink_page_list()
uses for iteration. Also, a page can't be marked as PageUnevictable(), when
it's attached to a shrinkable list.

So, the problem should be somewhere outside shrink_page_list().

I won't suggest you something about CMA, since I haven't dived in that code.

> We can add the unevictable pages in reclaim list in shrink_page_list(), return total number of reclaim pages including unevictable pages, let the caller handle unevictable pages.
> 
> I think the problem is shrink_page_list is awkard. If page is unevictable it goto activate_locked->keep_locked->keep lables, keep lable list_add the unevictable pages and throw the VM_BUG instead of passing it to caller while it relies on caller for non-reclaimed-non-unevictable  page's putback.
> I think we can make it consistent so that shrink_page_list could return non-reclaimed pages via page_list and caller can handle it. As an advance, it could try to migrate mlocked pages without retrial.
> 
> 
> Below is the issue of CMA_ALLOC of large size buffer : (Kernel version - 4.14.65 (On Android pie [ARM])).
> 
> [   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
> [   24.726949] page->mem_cgroup:bd008c00
> [   24.730693] ------------[ cut here ]------------
> [   24.735304] kernel BUG at mm/vmscan.c:1350!
> [   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
> 
> 
> Below is the patch which solved this issue :
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index be56e2e..12ac353 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>                 sc->nr_scanned++;
>  
>                 if (unlikely(!page_evictable(page)))
> -                       goto activate_locked;
> +                      goto cull_mlocked;
>  
>                 if (!sc->may_unmap && page_mapped(page))
>                         goto keep_locked;
> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>                 } else
>                         list_add(&page->lru, &free_pages);
>                 continue;
> -
> +cull_mlocked:
> +                if (PageSwapCache(page))
> +                        try_to_free_swap(page);
> +                unlock_page(page);
> +                list_add(&page->lru, &ret_pages);
> +                continue;
>  activate_locked:
>                 /* Not a candidate for swapping, so reclaim swap space. */
>                 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
> 
> 
> 
> 
> It fixes the below issue.
> 
> 1. Large size buffer allocation using cma_alloc successful with unevictable pages.
> 
> cma_alloc of current kernel will fail due to unevictable page
> 
> Please let me know if anything i am missing.
> 
> Regards,
> Pankaj
>   
> From: Vlastimil Babka <vbabka@suse.cz>
> Sent: 18 March 2019 14:12:50
> To: Pankaj Suryawanshi; Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>   
> 
> On 3/15/19 11:11 AM, Pankaj Suryawanshi wrote:
>>
>> [ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]
> 
> Can you send a proper patch with changelog explaining the change? I
> don't know the context of this thread.
> 
>> From: Pankaj Suryawanshi
>> Sent: 15 March 2019 11:35:05
>> To: Kirill Tkhai; Michal Hocko
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>
>>
>>
>> [ cc linux-mm ]
>>
>>
>> From: Pankaj Suryawanshi
>> Sent: 14 March 2019 19:14:40
>> To: Kirill Tkhai; Michal Hocko
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>
>>
>>
>> Hello ,
>>
>> Please ignore the curly braces, they are just for debugging.
>>
>> Below is the updated patch.
>>
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index be56e2e..12ac353 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                  sc->nr_scanned++;
>>
>>                  if (unlikely(!page_evictable(page)))
>> -                       goto activate_locked;
>> +                      goto cull_mlocked;
>>
>>                  if (!sc->may_unmap && page_mapped(page))
>>                          goto keep_locked;
>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                  } else
>>                          list_add(&page->lru, &free_pages);
>>                  continue;
>> -
>> +cull_mlocked:
>> +                if (PageSwapCache(page))
>> +                        try_to_free_swap(page);
>> +                unlock_page(page);
>> +                list_add(&page->lru, &ret_pages);
>> +                continue;
>>   activate_locked:
>>                  /* Not a candidate for swapping, so reclaim swap space. */
>>                  if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>
>>
>>
>> Regards,
>> Pankaj
>>
>>
>> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>> Sent: 14 March 2019 14:55:34
>> To: Pankaj Suryawanshi; Michal Hocko
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>
>>
>> On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>>>
>>> I am using kernel version 4.14.65 (on Android pie [ARM]).
>>>
>>> No additional patches applied on top of vanilla.(Core MM).
>>>
>>> If  I change in the vmscan.c as below patch, it will work.
>>
>> Sorry, but 4.14.65 does not have braces around trylock_page(),
>> like in your patch below.
>>
>> See      https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65
>>
>> [...]
>>
>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>> index be56e2e..2e51edc 100644
>>>> --- a/mm/vmscan.c
>>>> +++ b/mm/vmscan.c
>>>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>                   page = lru_to_page(page_list);
>>>>                   list_del(&page->lru);
>>>>
>>>>                  if (!trylock_page(page)) {
>>>>                           goto keep;
>>>>                  }
>>
>> ************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are intended  solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you  are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and please  delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage caused  by any virus transmitted by this email. *************************************************************************************************************************************************************
>>
> 
>     
> 

Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

Hi Kirill Tkhai,

Please see mm/vmscan.c in which it first added to list and than throw the error :
--------------------------------------------------------------------------------------------------
keep:
                list_add(&page->lru, &ret_pages);
                VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
---------------------------------------------------------------------------------------------------

Before throwing error, pages are added to list, this is under iteration of shrink_page_list().

From: Kirill Tkhai <ktkhai@virtuozzo.com>
Sent: 18 March 2019 15:03:15
To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
  

Hi, Pankaj,

On 18.03.2019 12:09, Pankaj Suryawanshi wrote:
> 
> Hello
> 
> shrink_page_list() returns , number of pages reclaimed, when pages is unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),page);

the general idea is shrink_page_list() can't iterate PageUnevictable() pages.
PageUnevictable() pages are never being added to lists, which shrink_page_list()
uses for iteration. Also, a page can't be marked as PageUnevictable(), when
it's attached to a shrinkable list.

So, the problem should be somewhere outside shrink_page_list().

I won't suggest you something about CMA, since I haven't dived in that code.

> We can add the unevictable pages in reclaim list in shrink_page_list(), return total number of reclaim pages including unevictable pages, let the caller handle unevictable pages.
> 
> I think the problem is shrink_page_list is awkard. If page is unevictable it goto activate_locked->keep_locked->keep lables, keep lable list_add the unevictable pages and throw the VM_BUG instead of passing it to caller while it relies on caller for non-reclaimed-non-unevictable   page's putback.
> I think we can make it consistent so that shrink_page_list could return non-reclaimed pages via page_list and caller can handle it. As an advance, it could try to migrate mlocked pages without retrial.
> 
> 
> Below is the issue of CMA_ALLOC of large size buffer : (Kernel version - 4.14.65 (On Android pie [ARM])).
> 
> [   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
> [   24.726949] page->mem_cgroup:bd008c00
> [   24.730693] ------------[ cut here ]------------
> [   24.735304] kernel BUG at mm/vmscan.c:1350!
> [   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
> 
> 
> Below is the patch which solved this issue :
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index be56e2e..12ac353 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>                 sc->nr_scanned++;
>  
>                 if (unlikely(!page_evictable(page)))
> -                       goto activate_locked;
> +                      goto cull_mlocked;
>  
>                 if (!sc->may_unmap && page_mapped(page))
>                         goto keep_locked;
> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>                 } else
>                         list_add(&page->lru, &free_pages);
>                 continue;
> -
> +cull_mlocked:
> +                if (PageSwapCache(page))
> +                        try_to_free_swap(page);
> +                unlock_page(page);
> +                list_add(&page->lru, &ret_pages);
> +                continue;
>  activate_locked:
>                 /* Not a candidate for swapping, so reclaim swap space. */
>                 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
> 
> 
> 
> 
> It fixes the below issue.
> 
> 1. Large size buffer allocation using cma_alloc successful with unevictable pages.
> 
> cma_alloc of current kernel will fail due to unevictable page
> 
> Please let me know if anything i am missing.
> 
> Regards,
> Pankaj
>   
> From: Vlastimil Babka <vbabka@suse.cz>
> Sent: 18 March 2019 14:12:50
> To: Pankaj Suryawanshi; Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>   
> 
> On 3/15/19 11:11 AM, Pankaj Suryawanshi wrote:
>>
>> [ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]
> 
> Can you send a proper patch with changelog explaining the change? I
> don't know the context of this thread.
> 
>> From: Pankaj Suryawanshi
>> Sent: 15 March 2019 11:35:05
>> To: Kirill Tkhai; Michal Hocko
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>
>>
>>
>> [ cc linux-mm ]
>>
>>
>> From: Pankaj Suryawanshi
>> Sent: 14 March 2019 19:14:40
>> To: Kirill Tkhai; Michal Hocko
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>
>>
>>
>> Hello ,
>>
>> Please ignore the curly braces, they are just for debugging.
>>
>> Below is the updated patch.
>>
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index be56e2e..12ac353 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                  sc->nr_scanned++;
>>
>>                  if (unlikely(!page_evictable(page)))
>> -                       goto activate_locked;
>> +                      goto cull_mlocked;
>>
>>                  if (!sc->may_unmap && page_mapped(page))
>>                          goto keep_locked;
>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                  } else
>>                          list_add(&page->lru, &free_pages);
>>                  continue;
>> -
>> +cull_mlocked:
>> +                if (PageSwapCache(page))
>> +                        try_to_free_swap(page);
>> +                unlock_page(page);
>> +                list_add(&page->lru, &ret_pages);
>> +                continue;
>>   activate_locked:
>>                  /* Not a candidate for swapping, so reclaim swap space. */
>>                  if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>
>>
>>
>> Regards,
>> Pankaj
>>
>>
>> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>> Sent: 14 March 2019 14:55:34
>> To: Pankaj Suryawanshi; Michal Hocko
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>
>>
>> On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>>>
>>> I am using kernel version 4.14.65 (on Android pie [ARM]).
>>>
>>> No additional patches applied on top of vanilla.(Core MM).
>>>
>>> If  I change in the vmscan.c as below patch, it will work.
>>
>> Sorry, but 4.14.65 does not have braces around trylock_page(),
>> like in your patch below.
>>
>> See       https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65
>>
>> [...]
>>
>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>> index be56e2e..2e51edc 100644
>>>> --- a/mm/vmscan.c
>>>> +++ b/mm/vmscan.c
>>>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>                   page = lru_to_page(page_list);
>>>>                   list_del(&page->lru);
>>>>
>>>>                  if (!trylock_page(page)) {
>>>>                           goto keep;
>>>>                  }
>>
>> ************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are  intended  solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient,  you  are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and  please  delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage  caused  by any virus transmitted by this email. *************************************************************************************************************************************************************
>>
> 
>     
> 
    

Re: [External] Re: vmscan: Reclaim unevictable pages

[Kirill Tkhai]

On 18.03.2019 12:43, Pankaj Suryawanshi wrote:
> Hi Kirill Tkhai,
>

Please, do not top posting: https://kernelnewbies.org/mailinglistguidelines

> Please see mm/vmscan.c in which it first added to list and than throw the error :
> --------------------------------------------------------------------------------------------------
> keep:
>                 list_add(&page->lru, &ret_pages);
>                 VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
> ---------------------------------------------------------------------------------------------------
> 
> Before throwing error, pages are added to list, this is under iteration of shrink_page_list().

I say about about the list, which is passed to shrink_page_list() as first argument.

shrink_inactive_list()
{
	isolate_lru_pages(&page_list); // <-- you can't obtain unevictable pages here.
	shrink_page_list(&page_list);
}
 
> From: Kirill Tkhai <ktkhai@virtuozzo.com>
> Sent: 18 March 2019 15:03:15
> To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>   
> 
> Hi, Pankaj,
> 
> On 18.03.2019 12:09, Pankaj Suryawanshi wrote:
>>
>> Hello
>>
>> shrink_page_list() returns , number of pages reclaimed, when pages is unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),page);
> 
> the general idea is shrink_page_list() can't iterate PageUnevictable() pages.
> PageUnevictable() pages are never being added to lists, which shrink_page_list()
> uses for iteration. Also, a page can't be marked as PageUnevictable(), when
> it's attached to a shrinkable list.
> 
> So, the problem should be somewhere outside shrink_page_list().
> 
> I won't suggest you something about CMA, since I haven't dived in that code.
> 
>> We can add the unevictable pages in reclaim list in shrink_page_list(), return total number of reclaim pages including unevictable pages, let the caller handle unevictable pages.
>>
>> I think the problem is shrink_page_list is awkard. If page is unevictable it goto activate_locked->keep_locked->keep lables, keep lable list_add the unevictable pages and throw the VM_BUG instead of passing it to caller while it relies on caller for non-reclaimed-non-unevictable   page's putback.
>> I think we can make it consistent so that shrink_page_list could return non-reclaimed pages via page_list and caller can handle it. As an advance, it could try to migrate mlocked pages without retrial.
>>
>>
>> Below is the issue of CMA_ALLOC of large size buffer : (Kernel version - 4.14.65 (On Android pie [ARM])).
>>
>> [   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
>> [   24.726949] page->mem_cgroup:bd008c00
>> [   24.730693] ------------[ cut here ]------------
>> [   24.735304] kernel BUG at mm/vmscan.c:1350!
>> [   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>>
>>
>> Below is the patch which solved this issue :
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index be56e2e..12ac353 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                 sc->nr_scanned++;
>>  
>>                 if (unlikely(!page_evictable(page)))
>> -                       goto activate_locked;
>> +                      goto cull_mlocked;
>>  
>>                 if (!sc->may_unmap && page_mapped(page))
>>                         goto keep_locked;
>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                 } else
>>                         list_add(&page->lru, &free_pages);
>>                 continue;
>> -
>> +cull_mlocked:
>> +                if (PageSwapCache(page))
>> +                        try_to_free_swap(page);
>> +                unlock_page(page);
>> +                list_add(&page->lru, &ret_pages);
>> +                continue;
>>  activate_locked:
>>                 /* Not a candidate for swapping, so reclaim swap space. */
>>                 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>
>>
>>
>>
>> It fixes the below issue.
>>
>> 1. Large size buffer allocation using cma_alloc successful with unevictable pages.
>>
>> cma_alloc of current kernel will fail due to unevictable page
>>
>> Please let me know if anything i am missing.
>>
>> Regards,
>> Pankaj
>>    
>> From: Vlastimil Babka <vbabka@suse.cz>
>> Sent: 18 March 2019 14:12:50
>> To: Pankaj Suryawanshi; Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
>> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>>   
>>
>> On 3/15/19 11:11 AM, Pankaj Suryawanshi wrote:
>>>
>>> [ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]
>>
>> Can you send a proper patch with changelog explaining the change? I
>> don't know the context of this thread.
>>
>>> From: Pankaj Suryawanshi
>>> Sent: 15 March 2019 11:35:05
>>> To: Kirill Tkhai; Michal Hocko
>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>
>>>
>>>
>>> [ cc linux-mm ]
>>>
>>>
>>> From: Pankaj Suryawanshi
>>> Sent: 14 March 2019 19:14:40
>>> To: Kirill Tkhai; Michal Hocko
>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>
>>>
>>>
>>> Hello ,
>>>
>>> Please ignore the curly braces, they are just for debugging.
>>>
>>> Below is the updated patch.
>>>
>>>
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index be56e2e..12ac353 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                  sc->nr_scanned++;
>>>
>>>                  if (unlikely(!page_evictable(page)))
>>> -                       goto activate_locked;
>>> +                      goto cull_mlocked;
>>>
>>>                  if (!sc->may_unmap && page_mapped(page))
>>>                          goto keep_locked;
>>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                  } else
>>>                          list_add(&page->lru, &free_pages);
>>>                  continue;
>>> -
>>> +cull_mlocked:
>>> +                if (PageSwapCache(page))
>>> +                        try_to_free_swap(page);
>>> +                unlock_page(page);
>>> +                list_add(&page->lru, &ret_pages);
>>> +                continue;
>>>   activate_locked:
>>>                  /* Not a candidate for swapping, so reclaim swap space. */
>>>                  if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>>
>>>
>>>
>>> Regards,
>>> Pankaj
>>>
>>>
>>> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>>> Sent: 14 March 2019 14:55:34
>>> To: Pankaj Suryawanshi; Michal Hocko
>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>
>>>
>>> On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>>>>
>>>> I am using kernel version 4.14.65 (on Android pie [ARM]).
>>>>
>>>> No additional patches applied on top of vanilla.(Core MM).
>>>>
>>>> If  I change in the vmscan.c as below patch, it will work.
>>>
>>> Sorry, but 4.14.65 does not have braces around trylock_page(),
>>> like in your patch below.
>>>
>>> See       https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65
>>>
>>> [...]
>>>
>>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>>> index be56e2e..2e51edc 100644
>>>>> --- a/mm/vmscan.c
>>>>> +++ b/mm/vmscan.c
>>>>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>>                   page = lru_to_page(page_list);
>>>>>                   list_del(&page->lru);
>>>>>
>>>>>                  if (!trylock_page(page)) {
>>>>>                           goto keep;
>>>>>                  }
>>>
>>> ************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are  intended  solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient,  you  are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and  please  delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage  caused  by any virus transmitted by this email. *************************************************************************************************************************************************************
>>>
>>
>>      
>>
>     
> 

Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

  
From: Kirill Tkhai <ktkhai@virtuozzo.com>
Sent: 18 March 2019 15:17:56
To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
  

On 18.03.2019 12:43, Pankaj Suryawanshi wrote:
> Hi Kirill Tkhai,
>

Please, do not top posting:  https://kernelnewbies.org/mailinglistguidelines

Okay.

mailinglistguidelines - Linux Kernel Newbies
kernelnewbies.org
Set of FAQs for kernelnewbies mailing list. If you are new to this list please read this page before you go on your quest for squeezing all the knowledge from fellow members.

> Please see mm/vmscan.c in which it first added to list and than throw the error :
> --------------------------------------------------------------------------------------------------
> keep:
>                 list_add(&page->lru, &ret_pages);
>                 VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
> ---------------------------------------------------------------------------------------------------
> 
> Before throwing error, pages are added to list, this is under iteration of shrink_page_list().

I say about about the list, which is passed to shrink_page_list() as first argument.
Did you mean candidate list which is passed to shrink_page_list().

shrink_inactive_list()
{
        isolate_lru_pages(&page_list); // <-- you can't obtain unevictable pages here.
        shrink_page_list(&page_list);
}

below is the overview of flow of calls for your information.

cma_alloc() ->
alloc_contig_range() ->
start_isolate_page_range() ->
__alloc_contig_migrate_range() ->
isolate_migratepages_range() ->
reclaim_clean_pages_from_list() ->
shrink_page_list()
 
> From: Kirill Tkhai <ktkhai@virtuozzo.com>
> Sent: 18 March 2019 15:03:15
> To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>   
> 
> Hi, Pankaj,
> 
> On 18.03.2019 12:09, Pankaj Suryawanshi wrote:
>>
>> Hello
>>
>> shrink_page_list() returns , number of pages reclaimed, when pages is unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),page);
> 
> the general idea is shrink_page_list() can't iterate PageUnevictable() pages.
> PageUnevictable() pages are never being added to lists, which shrink_page_list()
> uses for iteration. Also, a page can't be marked as PageUnevictable(), when
> it's attached to a shrinkable list.
> 
> So, the problem should be somewhere outside shrink_page_list().
> 
> I won't suggest you something about CMA, since I haven't dived in that code.
> 
>> We can add the unevictable pages in reclaim list in shrink_page_list(), return total number of reclaim pages including unevictable pages, let the caller handle unevictable pages.
>>
>> I think the problem is shrink_page_list is awkard. If page is unevictable it goto activate_locked->keep_locked->keep lables, keep lable list_add the unevictable pages and throw the VM_BUG instead of passing it to caller while it relies on caller for non-reclaimed-non-unevictable    page's putback.
>> I think we can make it consistent so that shrink_page_list could return non-reclaimed pages via page_list and caller can handle it. As an advance, it could try to migrate mlocked pages without retrial.
>>
>>
>> Below is the issue of CMA_ALLOC of large size buffer : (Kernel version - 4.14.65 (On Android pie [ARM])).
>>
>> [   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
>> [   24.726949] page->mem_cgroup:bd008c00
>> [   24.730693] ------------[ cut here ]------------
>> [   24.735304] kernel BUG at mm/vmscan.c:1350!
>> [   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>>
>>
>> Below is the patch which solved this issue :
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index be56e2e..12ac353 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                 sc->nr_scanned++;
>>  
>>                 if (unlikely(!page_evictable(page)))
>> -                       goto activate_locked;
>> +                      goto cull_mlocked;
>>  
>>                 if (!sc->may_unmap && page_mapped(page))
>>                         goto keep_locked;
>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>                 } else
>>                         list_add(&page->lru, &free_pages);
>>                 continue;
>> -
>> +cull_mlocked:
>> +                if (PageSwapCache(page))
>> +                        try_to_free_swap(page);
>> +                unlock_page(page);
>> +                list_add(&page->lru, &ret_pages);
>> +                continue;
>>  activate_locked:
>>                 /* Not a candidate for swapping, so reclaim swap space. */
>>                 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>
>>
>>
>>
>> It fixes the below issue.
>>
>> 1. Large size buffer allocation using cma_alloc successful with unevictable pages.
>>
>> cma_alloc of current kernel will fail due to unevictable page
>>
>> Please let me know if anything i am missing.
>>
>> Regards,
>> Pankaj
>>    
>> From: Vlastimil Babka <vbabka@suse.cz>
>> Sent: 18 March 2019 14:12:50
>> To: Pankaj Suryawanshi; Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
>> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>>   
>>
>> On 3/15/19 11:11 AM, Pankaj Suryawanshi wrote:
>>>
>>> [ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]
>>
>> Can you send a proper patch with changelog explaining the change? I
>> don't know the context of this thread.
>>
>>> From: Pankaj Suryawanshi
>>> Sent: 15 March 2019 11:35:05
>>> To: Kirill Tkhai; Michal Hocko
>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>
>>>
>>>
>>> [ cc linux-mm ]
>>>
>>>
>>> From: Pankaj Suryawanshi
>>> Sent: 14 March 2019 19:14:40
>>> To: Kirill Tkhai; Michal Hocko
>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>
>>>
>>>
>>> Hello ,
>>>
>>> Please ignore the curly braces, they are just for debugging.
>>>
>>> Below is the updated patch.
>>>
>>>
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index be56e2e..12ac353 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                  sc->nr_scanned++;
>>>
>>>                  if (unlikely(!page_evictable(page)))
>>> -                       goto activate_locked;
>>> +                      goto cull_mlocked;
>>>
>>>                  if (!sc->may_unmap && page_mapped(page))
>>>                          goto keep_locked;
>>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                  } else
>>>                          list_add(&page->lru, &free_pages);
>>>                  continue;
>>> -
>>> +cull_mlocked:
>>> +                if (PageSwapCache(page))
>>> +                        try_to_free_swap(page);
>>> +                unlock_page(page);
>>> +                list_add(&page->lru, &ret_pages);
>>> +                continue;
>>>   activate_locked:
>>>                  /* Not a candidate for swapping, so reclaim swap space. */
>>>                  if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>>
>>>
>>>
>>> Regards,
>>> Pankaj
>>>
>>>
>>> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>>> Sent: 14 March 2019 14:55:34
>>> To: Pankaj Suryawanshi; Michal Hocko
>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>
>>>
>>> On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>>>>
>>>> I am using kernel version 4.14.65 (on Android pie [ARM]).
>>>>
>>>> No additional patches applied on top of vanilla.(Core MM).
>>>>
>>>> If  I change in the vmscan.c as below patch, it will work.
>>>
>>> Sorry, but 4.14.65 does not have braces around trylock_page(),
>>> like in your patch below.
>>>
>>> See        https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65
>>>
>>> [...]
>>>
>>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>>> index be56e2e..2e51edc 100644
>>>>> --- a/mm/vmscan.c
>>>>> +++ b/mm/vmscan.c
>>>>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>>                   page = lru_to_page(page_list);
>>>>>                   list_del(&page->lru);
>>>>>
>>>>>                  if (!trylock_page(page)) {
>>>>>                           goto keep;
>>>>>                  }
>>>
>>> ************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are   intended  solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient,   you  are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and   please  delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage   caused  by any virus transmitted by this email. *************************************************************************************************************************************************************
>>>
>>
>>      
>>
>     
> 
    

Re: [External] Re: vmscan: Reclaim unevictable pages

[Kirill Tkhai]

On 18.03.2019 12:59, Pankaj Suryawanshi wrote:
>   
> From: Kirill Tkhai <ktkhai@virtuozzo.com>
> Sent: 18 March 2019 15:17:56
> To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages

Also, please, avoid irritating quoting like below ^^^. They just distract attention.
 
> On 18.03.2019 12:43, Pankaj Suryawanshi wrote:
>> Hi Kirill Tkhai,
>>
> 
> Please, do not top posting:  https://kernelnewbies.org/mailinglistguidelines
> 
> Okay.
> 
> mailinglistguidelines - Linux Kernel Newbies
> kernelnewbies.org
> Set of FAQs for kernelnewbies mailing list. If you are new to this list please read this page before you go on your quest for squeezing all the knowledge from fellow members.

And this spew ^^^.

>> Please see mm/vmscan.c in which it first added to list and than throw the error :
>> --------------------------------------------------------------------------------------------------
>> keep:
>>                  list_add(&page->lru, &ret_pages);
>>                  VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
>> ---------------------------------------------------------------------------------------------------
>>
>> Before throwing error, pages are added to list, this is under iteration of shrink_page_list().
> 
> I say about about the list, which is passed to shrink_page_list() as first argument.
> Did you mean candidate list which is passed to shrink_page_list().
> 
> shrink_inactive_list()
> {
>         isolate_lru_pages(&page_list); // <-- you can't obtain unevictable pages here.
>         shrink_page_list(&page_list);
> }
> 
> below is the overview of flow of calls for your information.
> 
> cma_alloc() ->
> alloc_contig_range() ->
> start_isolate_page_range() ->
> __alloc_contig_migrate_range() ->
> isolate_migratepages_range() ->
> reclaim_clean_pages_from_list() ->
> shrink_page_list()

Hm, isolate_migratepages_range() can take unevictable pages,
but then with your patch we just skip them in shrink_page_list().
Without your patch we bump into bug on.

These both look incorrect for me. Let's wait someone who familiar
with this logic.
  
>> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>> Sent: 18 March 2019 15:03:15
>> To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
>> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>>   
>>
>> Hi, Pankaj,
>>
>> On 18.03.2019 12:09, Pankaj Suryawanshi wrote:
>>>
>>> Hello
>>>
>>> shrink_page_list() returns , number of pages reclaimed, when pages is unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),page);
>>
>> the general idea is shrink_page_list() can't iterate PageUnevictable() pages.
>> PageUnevictable() pages are never being added to lists, which shrink_page_list()
>> uses for iteration. Also, a page can't be marked as PageUnevictable(), when
>> it's attached to a shrinkable list.
>>
>> So, the problem should be somewhere outside shrink_page_list().
>>
>> I won't suggest you something about CMA, since I haven't dived in that code.
>>
>>> We can add the unevictable pages in reclaim list in shrink_page_list(), return total number of reclaim pages including unevictable pages, let the caller handle unevictable pages.
>>>
>>> I think the problem is shrink_page_list is awkard. If page is unevictable it goto activate_locked->keep_locked->keep lables, keep lable list_add the unevictable pages and throw the VM_BUG instead of passing it to caller while it relies on caller for non-reclaimed-non-unevictable    page's putback.
>>> I think we can make it consistent so that shrink_page_list could return non-reclaimed pages via page_list and caller can handle it. As an advance, it could try to migrate mlocked pages without retrial.
>>>
>>>
>>> Below is the issue of CMA_ALLOC of large size buffer : (Kernel version - 4.14.65 (On Android pie [ARM])).
>>>
>>> [   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
>>> [   24.726949] page->mem_cgroup:bd008c00
>>> [   24.730693] ------------[ cut here ]------------
>>> [   24.735304] kernel BUG at mm/vmscan.c:1350!
>>> [   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>>>
>>>
>>> Below is the patch which solved this issue :
>>>
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index be56e2e..12ac353 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                 sc->nr_scanned++;
>>>  
>>>                 if (unlikely(!page_evictable(page)))
>>> -                       goto activate_locked;
>>> +                      goto cull_mlocked;
>>>  
>>>                 if (!sc->may_unmap && page_mapped(page))
>>>                         goto keep_locked;
>>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                 } else
>>>                         list_add(&page->lru, &free_pages);
>>>                 continue;
>>> -
>>> +cull_mlocked:
>>> +                if (PageSwapCache(page))
>>> +                        try_to_free_swap(page);
>>> +                unlock_page(page);
>>> +                list_add(&page->lru, &ret_pages);
>>> +                continue;
>>>  activate_locked:
>>>                 /* Not a candidate for swapping, so reclaim swap space. */
>>>                 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>>
>>>
>>>
>>>
>>> It fixes the below issue.
>>>
>>> 1. Large size buffer allocation using cma_alloc successful with unevictable pages.
>>>
>>> cma_alloc of current kernel will fail due to unevictable page
>>>
>>> Please let me know if anything i am missing.
>>>
>>> Regards,
>>> Pankaj
>>>    
>>> From: Vlastimil Babka <vbabka@suse.cz>
>>> Sent: 18 March 2019 14:12:50
>>> To: Pankaj Suryawanshi; Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
>>> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>   
>>>
>>> On 3/15/19 11:11 AM, Pankaj Suryawanshi wrote:
>>>>
>>>> [ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]
>>>
>>> Can you send a proper patch with changelog explaining the change? I
>>> don't know the context of this thread.
>>>
>>>> From: Pankaj Suryawanshi
>>>> Sent: 15 March 2019 11:35:05
>>>> To: Kirill Tkhai; Michal Hocko
>>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
>>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>>
>>>>
>>>>
>>>> [ cc linux-mm ]
>>>>
>>>>
>>>> From: Pankaj Suryawanshi
>>>> Sent: 14 March 2019 19:14:40
>>>> To: Kirill Tkhai; Michal Hocko
>>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>>
>>>>
>>>>
>>>> Hello ,
>>>>
>>>> Please ignore the curly braces, they are just for debugging.
>>>>
>>>> Below is the updated patch.
>>>>
>>>>
>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>> index be56e2e..12ac353 100644
>>>> --- a/mm/vmscan.c
>>>> +++ b/mm/vmscan.c
>>>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>                  sc->nr_scanned++;
>>>>
>>>>                  if (unlikely(!page_evictable(page)))
>>>> -                       goto activate_locked;
>>>> +                      goto cull_mlocked;
>>>>
>>>>                  if (!sc->may_unmap && page_mapped(page))
>>>>                          goto keep_locked;
>>>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>                  } else
>>>>                          list_add(&page->lru, &free_pages);
>>>>                  continue;
>>>> -
>>>> +cull_mlocked:
>>>> +                if (PageSwapCache(page))
>>>> +                        try_to_free_swap(page);
>>>> +                unlock_page(page);
>>>> +                list_add(&page->lru, &ret_pages);
>>>> +                continue;
>>>>   activate_locked:
>>>>                  /* Not a candidate for swapping, so reclaim swap space. */
>>>>                  if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>>>
>>>>
>>>>
>>>> Regards,
>>>> Pankaj
>>>>
>>>>
>>>> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>>>> Sent: 14 March 2019 14:55:34
>>>> To: Pankaj Suryawanshi; Michal Hocko
>>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>>
>>>>
>>>> On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>>>>>
>>>>> I am using kernel version 4.14.65 (on Android pie [ARM]).
>>>>>
>>>>> No additional patches applied on top of vanilla.(Core MM).
>>>>>
>>>>> If  I change in the vmscan.c as below patch, it will work.
>>>>
>>>> Sorry, but 4.14.65 does not have braces around trylock_page(),
>>>> like in your patch below.
>>>>
>>>> See        https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65
>>>>
>>>> [...]
>>>>
>>>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>>>> index be56e2e..2e51edc 100644
>>>>>> --- a/mm/vmscan.c
>>>>>> +++ b/mm/vmscan.c
>>>>>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>>>                   page = lru_to_page(page_list);
>>>>>>                   list_del(&page->lru);
>>>>>>
>>>>>>                  if (!trylock_page(page)) {
>>>>>>                           goto keep;
>>>>>>                  }
>>>>
>>>> ************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are   intended  solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient,   you  are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and   please  delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage   caused  by any virus transmitted by this email. *************************************************************************************************************************************************************
>>>>
>>>
>>>      
>>>
>>      
>>
>     
> 

Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

________________________________________
From: Kirill Tkhai <ktkhai@virtuozzo.com>
Sent: 18 March 2019 16:08
To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com
Subject: Re: [External] Re: vmscan: Reclaim unevictable pages

On 18.03.2019 12:59, Pankaj Suryawanshi wrote:
>
> From: Kirill Tkhai <ktkhai@virtuozzo.com>
> Sent: 18 March 2019 15:17:56
> To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages

Also, please, avoid irritating quoting like below ^^^. They just distract attention.

> On 18.03.2019 12:43, Pankaj Suryawanshi wrote:
>> Hi Kirill Tkhai,
>>
>
> Please, do not top posting:  https://kernelnewbies.org/mailinglistguidelines
>
> Okay.
>
> mailinglistguidelines - Linux Kernel Newbies
> kernelnewbies.org
> Set of FAQs for kernelnewbies mailing list. If you are new to this list please read this page before you go on your quest for squeezing all the knowledge from fellow members.

And this spew ^^^.

>> Please see mm/vmscan.c in which it first added to list and than throw the error :
>> --------------------------------------------------------------------------------------------------
>> keep:
>>                  list_add(&page->lru, &ret_pages);
>>                  VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
>> ---------------------------------------------------------------------------------------------------
>>
>> Before throwing error, pages are added to list, this is under iteration of shrink_page_list().
>
> I say about about the list, which is passed to shrink_page_list() as first argument.
> Did you mean candidate list which is passed to shrink_page_list().
>
> shrink_inactive_list()
> {
>         isolate_lru_pages(&page_list); // <-- you can't obtain unevictable pages here.
>         shrink_page_list(&page_list);
> }
>
> below is the overview of flow of calls for your information.
>
> cma_alloc() ->
> alloc_contig_range() ->
> start_isolate_page_range() ->
> __alloc_contig_migrate_range() ->
> isolate_migratepages_range() ->
> reclaim_clean_pages_from_list() ->
> shrink_page_list()

Hm, isolate_migratepages_range() can take unevictable pages,
but then with your patch we just skip them in shrink_page_list().
Without your patch we bump into bug on.

I don't see any other issue/effect if i apply this patch.

These both look incorrect for me. Let's wait someone who familiar
with this logic.

>> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>> Sent: 18 March 2019 15:03:15
>> To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
>> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>>
>>
>> Hi, Pankaj,
>>
>> On 18.03.2019 12:09, Pankaj Suryawanshi wrote:
>>>
>>> Hello
>>>
>>> shrink_page_list() returns , number of pages reclaimed, when pages is unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),page);
>>
>> the general idea is shrink_page_list() can't iterate PageUnevictable() pages.
>> PageUnevictable() pages are never being added to lists, which shrink_page_list()
>> uses for iteration. Also, a page can't be marked as PageUnevictable(), when
>> it's attached to a shrinkable list.
>>
>> So, the problem should be somewhere outside shrink_page_list().
>>
>> I won't suggest you something about CMA, since I haven't dived in that code.
>>
>>> We can add the unevictable pages in reclaim list in shrink_page_list(), return total number of reclaim pages including unevictable pages, let the caller handle unevictable pages.
>>>
>>> I think the problem is shrink_page_list is awkard. If page is unevictable it goto activate_locked->keep_locked->keep lables, keep lable list_add the unevictable pages and throw the VM_BUG instead of passing it to caller while it relies on caller for non-reclaimed-non-unevictable    page's putback.
>>> I think we can make it consistent so that shrink_page_list could return non-reclaimed pages via page_list and caller can handle it. As an advance, it could try to migrate mlocked pages without retrial.
>>>
>>>
>>> Below is the issue of CMA_ALLOC of large size buffer : (Kernel version - 4.14.65 (On Android pie [ARM])).
>>>
>>> [   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
>>> [   24.726949] page->mem_cgroup:bd008c00
>>> [   24.730693] ------------[ cut here ]------------
>>> [   24.735304] kernel BUG at mm/vmscan.c:1350!
>>> [   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>>>
>>>
>>> Below is the patch which solved this issue :
>>>
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index be56e2e..12ac353 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                 sc->nr_scanned++;
>>>
>>>                 if (unlikely(!page_evictable(page)))
>>> -                       goto activate_locked;
>>> +                      goto cull_mlocked;
>>>
>>>                 if (!sc->may_unmap && page_mapped(page))
>>>                         goto keep_locked;
>>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                 } else
>>>                         list_add(&page->lru, &free_pages);
>>>                 continue;
>>> -
>>> +cull_mlocked:
>>> +                if (PageSwapCache(page))
>>> +                        try_to_free_swap(page);
>>> +                unlock_page(page);
>>> +                list_add(&page->lru, &ret_pages);
>>> +                continue;
>>>  activate_locked:
>>>                 /* Not a candidate for swapping, so reclaim swap space. */
>>>                 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>>
>>>
>>>
>>>
>>> It fixes the below issue.
>>>
>>> 1. Large size buffer allocation using cma_alloc successful with unevictable pages.
>>>
>>> cma_alloc of current kernel will fail due to unevictable page
>>>
>>> Please let me know if anything i am missing.
>>>
>>> Regards,
>>> Pankaj
>>>
>>> From: Vlastimil Babka <vbabka@suse.cz>
>>> Sent: 18 March 2019 14:12:50
>>> To: Pankaj Suryawanshi; Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
>>> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>
>>>
>>> On 3/15/19 11:11 AM, Pankaj Suryawanshi wrote:
>>>>
>>>> [ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]
>>>
>>> Can you send a proper patch with changelog explaining the change? I
>>> don't know the context of this thread.
>>>
>>>> From: Pankaj Suryawanshi
>>>> Sent: 15 March 2019 11:35:05
>>>> To: Kirill Tkhai; Michal Hocko
>>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
>>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>>
>>>>
>>>>
>>>> [ cc linux-mm ]
>>>>
>>>>
>>>> From: Pankaj Suryawanshi
>>>> Sent: 14 March 2019 19:14:40
>>>> To: Kirill Tkhai; Michal Hocko
>>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>>
>>>>
>>>>
>>>> Hello ,
>>>>
>>>> Please ignore the curly braces, they are just for debugging.
>>>>
>>>> Below is the updated patch.
>>>>
>>>>
>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>> index be56e2e..12ac353 100644
>>>> --- a/mm/vmscan.c
>>>> +++ b/mm/vmscan.c
>>>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>                  sc->nr_scanned++;
>>>>
>>>>                  if (unlikely(!page_evictable(page)))
>>>> -                       goto activate_locked;
>>>> +                      goto cull_mlocked;
>>>>
>>>>                  if (!sc->may_unmap && page_mapped(page))
>>>>                          goto keep_locked;
>>>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>                  } else
>>>>                          list_add(&page->lru, &free_pages);
>>>>                  continue;
>>>> -
>>>> +cull_mlocked:
>>>> +                if (PageSwapCache(page))
>>>> +                        try_to_free_swap(page);
>>>> +                unlock_page(page);
>>>> +                list_add(&page->lru, &ret_pages);
>>>> +                continue;
>>>>   activate_locked:
>>>>                  /* Not a candidate for swapping, so reclaim swap space. */
>>>>                  if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>>>
>>>>
>>>>
>>>> Regards,
>>>> Pankaj
>>>>
>>>>
>>>> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>>>> Sent: 14 March 2019 14:55:34
>>>> To: Pankaj Suryawanshi; Michal Hocko
>>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>>
>>>>
>>>> On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>>>>>
>>>>> I am using kernel version 4.14.65 (on Android pie [ARM]).
>>>>>
>>>>> No additional patches applied on top of vanilla.(Core MM).
>>>>>
>>>>> If  I change in the vmscan.c as below patch, it will work.
>>>>
>>>> Sorry, but 4.14.65 does not have braces around trylock_page(),
>>>> like in your patch below.
>>>>
>>>> See        https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65
>>>>
>>>> [...]
>>>>
>>>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>>>> index be56e2e..2e51edc 100644
>>>>>> --- a/mm/vmscan.c
>>>>>> +++ b/mm/vmscan.c
>>>>>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>>>                   page = lru_to_page(page_list);
>>>>>>                   list_del(&page->lru);
>>>>>>
>>>>>>                  if (!trylock_page(page)) {
>>>>>>                           goto keep;
>>>>>>                  }
>>>>
>>>> ************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are   intended  solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient,   you  are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and   please  delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage   caused  by any virus transmitted by this email. *************************************************************************************************************************************************************
>>>>
>>>
>>>
>>>
>>
>>
>
>

Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

________________________________________
From: Pankaj Suryawanshi
Sent: 20 March 2019 12:18
To: Kirill Tkhai; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com
Subject: Re: [External] Re: vmscan: Reclaim unevictable pages


________________________________________
From: Kirill Tkhai <ktkhai@virtuozzo.com>
Sent: 18 March 2019 16:08
To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com
Subject: Re: [External] Re: vmscan: Reclaim unevictable pages

On 18.03.2019 12:59, Pankaj Suryawanshi wrote:
>
> From: Kirill Tkhai <ktkhai@virtuozzo.com>
> Sent: 18 March 2019 15:17:56
> To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages

Also, please, avoid irritating quoting like below ^^^. They just distract attention.

> On 18.03.2019 12:43, Pankaj Suryawanshi wrote:
>> Hi Kirill Tkhai,
>>
>
> Please, do not top posting:  https://kernelnewbies.org/mailinglistguidelines
>
> Okay.
>
> mailinglistguidelines - Linux Kernel Newbies
> kernelnewbies.org
> Set of FAQs for kernelnewbies mailing list. If you are new to this list please read this page before you go on your quest for squeezing all the knowledge from fellow members.

And this spew ^^^.

>> Please see mm/vmscan.c in which it first added to list and than throw the error :
>> --------------------------------------------------------------------------------------------------
>> keep:
>>                  list_add(&page->lru, &ret_pages);
>>                  VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
>> ---------------------------------------------------------------------------------------------------
>>
>> Before throwing error, pages are added to list, this is under iteration of shrink_page_list().
>
> I say about about the list, which is passed to shrink_page_list() as first argument.
> Did you mean candidate list which is passed to shrink_page_list().
>
> shrink_inactive_list()
> {
>         isolate_lru_pages(&page_list); // <-- you can't obtain unevictable pages here.
>         shrink_page_list(&page_list);
> }
>
> below is the overview of flow of calls for your information.
>
> cma_alloc() ->
> alloc_contig_range() ->
> start_isolate_page_range() ->
> __alloc_contig_migrate_range() ->
> isolate_migratepages_range() ->
> reclaim_clean_pages_from_list() ->
> shrink_page_list()

Hm, isolate_migratepages_range() can take unevictable pages,
but then with your patch we just skip them in shrink_page_list().
Without your patch we bump into bug on.

I don't see any other issue/effect if i apply this patch.

These both look incorrect for me. Let's wait someone who familiar
with this logic.

Is there anyone who is familiar with this?  Please Comment.

>> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>> Sent: 18 March 2019 15:03:15
>> To: Pankaj Suryawanshi; Vlastimil Babka; Michal Hocko; aneesh.kumar@linux.ibm.com
>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
>> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>>
>>
>> Hi, Pankaj,
>>
>> On 18.03.2019 12:09, Pankaj Suryawanshi wrote:
>>>
>>> Hello
>>>
>>> shrink_page_list() returns , number of pages reclaimed, when pages is unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),page);
>>
>> the general idea is shrink_page_list() can't iterate PageUnevictable() pages.
>> PageUnevictable() pages are never being added to lists, which shrink_page_list()
>> uses for iteration. Also, a page can't be marked as PageUnevictable(), when
>> it's attached to a shrinkable list.
>>
>> So, the problem should be somewhere outside shrink_page_list().
>>
>> I won't suggest you something about CMA, since I haven't dived in that code.
>>
>>> We can add the unevictable pages in reclaim list in shrink_page_list(), return total number of reclaim pages including unevictable pages, let the caller handle unevictable pages.
>>>
>>> I think the problem is shrink_page_list is awkard. If page is unevictable it goto activate_locked->keep_locked->keep lables, keep lable list_add the unevictable pages and throw the VM_BUG instead of passing it to caller while it relies on caller for non-reclaimed-non-unevictable    page's putback.
>>> I think we can make it consistent so that shrink_page_list could return non-reclaimed pages via page_list and caller can handle it. As an advance, it could try to migrate mlocked pages without retrial.
>>>
>>>
>>> Below is the issue of CMA_ALLOC of large size buffer : (Kernel version - 4.14.65 (On Android pie [ARM])).
>>>
>>> [   24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page))
>>> [   24.726949] page->mem_cgroup:bd008c00
>>> [   24.730693] ------------[ cut here ]------------
>>> [   24.735304] kernel BUG at mm/vmscan.c:1350!
>>> [   24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>>>
>>>
>>> Below is the patch which solved this issue :
>>>
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index be56e2e..12ac353 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                 sc->nr_scanned++;
>>>
>>>                 if (unlikely(!page_evictable(page)))
>>> -                       goto activate_locked;
>>> +                      goto cull_mlocked;
>>>
>>>                 if (!sc->may_unmap && page_mapped(page))
>>>                         goto keep_locked;
>>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>                 } else
>>>                         list_add(&page->lru, &free_pages);
>>>                 continue;
>>> -
>>> +cull_mlocked:
>>> +                if (PageSwapCache(page))
>>> +                        try_to_free_swap(page);
>>> +                unlock_page(page);
>>> +                list_add(&page->lru, &ret_pages);
>>> +                continue;
>>>  activate_locked:
>>>                 /* Not a candidate for swapping, so reclaim swap space. */
>>>                 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>>
>>>
>>>
>>>
>>> It fixes the below issue.
>>>
>>> 1. Large size buffer allocation using cma_alloc successful with unevictable pages.
>>>
>>> cma_alloc of current kernel will fail due to unevictable page
>>>
>>> Please let me know if anything i am missing.
>>>
>>> Regards,
>>> Pankaj
>>>
>>> From: Vlastimil Babka <vbabka@suse.cz>
>>> Sent: 18 March 2019 14:12:50
>>> To: Pankaj Suryawanshi; Kirill Tkhai; Michal Hocko; aneesh.kumar@linux.ibm.com
>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com; hillf.zj@alibaba-inc.com
>>> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>
>>>
>>> On 3/15/19 11:11 AM, Pankaj Suryawanshi wrote:
>>>>
>>>> [ cc Aneesh kumar, Anshuman, Hillf, Vlastimil]
>>>
>>> Can you send a proper patch with changelog explaining the change? I
>>> don't know the context of this thread.
>>>
>>>> From: Pankaj Suryawanshi
>>>> Sent: 15 March 2019 11:35:05
>>>> To: Kirill Tkhai; Michal Hocko
>>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org
>>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>>
>>>>
>>>>
>>>> [ cc linux-mm ]
>>>>
>>>>
>>>> From: Pankaj Suryawanshi
>>>> Sent: 14 March 2019 19:14:40
>>>> To: Kirill Tkhai; Michal Hocko
>>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>>
>>>>
>>>>
>>>> Hello ,
>>>>
>>>> Please ignore the curly braces, they are just for debugging.
>>>>
>>>> Below is the updated patch.
>>>>
>>>>
>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>> index be56e2e..12ac353 100644
>>>> --- a/mm/vmscan.c
>>>> +++ b/mm/vmscan.c
>>>> @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>                  sc->nr_scanned++;
>>>>
>>>>                  if (unlikely(!page_evictable(page)))
>>>> -                       goto activate_locked;
>>>> +                      goto cull_mlocked;
>>>>
>>>>                  if (!sc->may_unmap && page_mapped(page))
>>>>                          goto keep_locked;
>>>> @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>                  } else
>>>>                          list_add(&page->lru, &free_pages);
>>>>                  continue;
>>>> -
>>>> +cull_mlocked:
>>>> +                if (PageSwapCache(page))
>>>> +                        try_to_free_swap(page);
>>>> +                unlock_page(page);
>>>> +                list_add(&page->lru, &ret_pages);
>>>> +                continue;
>>>>   activate_locked:
>>>>                  /* Not a candidate for swapping, so reclaim swap space. */
>>>>                  if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
>>>>
>>>>
>>>>
>>>> Regards,
>>>> Pankaj
>>>>
>>>>
>>>> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>>>> Sent: 14 March 2019 14:55:34
>>>> To: Pankaj Suryawanshi; Michal Hocko
>>>> Cc: linux-kernel@vger.kernel.org; minchan@kernel.org
>>>> Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages
>>>>
>>>>
>>>> On 14.03.2019 11:52, Pankaj Suryawanshi wrote:
>>>>>
>>>>> I am using kernel version 4.14.65 (on Android pie [ARM]).
>>>>>
>>>>> No additional patches applied on top of vanilla.(Core MM).
>>>>>
>>>>> If  I change in the vmscan.c as below patch, it will work.
>>>>
>>>> Sorry, but 4.14.65 does not have braces around trylock_page(),
>>>> like in your patch below.
>>>>
>>>> See        https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65
>>>>
>>>> [...]
>>>>
>>>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>>>> index be56e2e..2e51edc 100644
>>>>>> --- a/mm/vmscan.c
>>>>>> +++ b/mm/vmscan.c
>>>>>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>>>>>>                   page = lru_to_page(page_list);
>>>>>>                   list_del(&page->lru);
>>>>>>
>>>>>>                  if (!trylock_page(page)) {
>>>>>>                           goto keep;
>>>>>>                  }
>>>>
>>>> ************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are   intended  solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient,   you  are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and   please  delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage   caused  by any virus transmitted by this email. *************************************************************************************************************************************************************
>>>>
>>>
>>>
>>>
>>
>>
>
>

Re: [External] Re: vmscan: Reclaim unevictable pages

[Michal Hocko]

[You were asked to use a reasonable quoting several times. This is
really annoying because it turns the email thread into a complete mess]

On Tue 26-03-19 07:53:14, Pankaj Suryawanshi wrote:
> Is there anyone who is familiar with this?  Please Comment.

Not really. You are observing an unexpected behavior of the page reclaim
which hasn't changed for quite some time. So I find more probable that
your non-vanilla kernel is doing something unexpected. It would help if
you could track down how does the unevictable page get down to the
reclaim path. I assume this is a CMA page or something like that but
those shouldn't get to the reclaim path AFIR.
-- 
Michal Hocko
SUSE Labs

Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

________________________________________
From: Michal Hocko <mhocko@kernel.org>
Sent: 26 March 2019 14:31
To: Pankaj Suryawanshi
Cc: Kirill Tkhai; Vlastimil Babka; aneesh.kumar@linux.ibm.com; linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com
Subject: Re: [External] Re: vmscan: Reclaim unevictable pages

[You were asked to use a reasonable quoting several times. This is
really annoying because it turns the email thread into a complete mess]

I already fix the email client, dont know the reason for quoting.

On Tue 26-03-19 07:53:14, Pankaj Suryawanshi wrote:
> Is there anyone who is familiar with this?  Please Comment.

Not really. You are observing an unexpected behavior of the page reclaim
which hasn't changed for quite some time. So I find more probable that
your non-vanilla kernel is doing something unexpected. It would help if
you could track down how does the unevictable page get down to the
reclaim path. I assume this is a CMA page or something like that but
those shouldn't get to the reclaim path AFIR.

As i said earlier, the kernel i am using is vanilla kernel.

--
Michal Hocko
SUSE Labs
************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are intended solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and please delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage caused by any virus transmitted by this email. *************************************************************************************************************************************************************

Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

________________________________________
From: Michal Hocko <mhocko@kernel.org>
Sent: 26 March 2019 14:31
To: Pankaj Suryawanshi
Cc: Kirill Tkhai; Vlastimil Babka; aneesh.kumar@linux.ibm.com; linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com
Subject: Re: [External] Re: vmscan: Reclaim unevictable pages

[You were asked to use a reasonable quoting several times. This is
really annoying because it turns the email thread into a complete mess]

[Already fix the email client, but dont know the reason for quoting Maybe account issue.]

On Tue 26-03-19 07:53:14, Pankaj Suryawanshi wrote:
> Is there anyone who is familiar with this?  Please Comment.

Not really. You are observing an unexpected behavior of the page reclaim
which hasn't changed for quite some time. So I find more probable that
your non-vanilla kernel is doing something unexpected. It would help if
you could track down how does the unevictable page get down to the
reclaim path. I assume this is a CMA page or something like that but
those shouldn't get to the reclaim path AFIR.

As i said earlier, i am using vanilla kernel 4.14.65.
--
Michal Hocko
SUSE Labs
************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are intended solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and please delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage caused by any virus transmitted by this email. *************************************************************************************************************************************************************

Re: [External] Re: vmscan: Reclaim unevictable pages

[Michal Hocko]

On Tue 26-03-19 09:16:11, Pankaj Suryawanshi wrote:
> 
> ________________________________________
> From: Michal Hocko <mhocko@kernel.org>
> Sent: 26 March 2019 14:31
> To: Pankaj Suryawanshi
> Cc: Kirill Tkhai; Vlastimil Babka; aneesh.kumar@linux.ibm.com; linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com
> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
> 
> [You were asked to use a reasonable quoting several times. This is
> really annoying because it turns the email thread into a complete mess]
> 
> [Already fix the email client, but dont know the reason for quoting Maybe account issue.]

You clearly haven't

> As i said earlier, i am using vanilla kernel 4.14.65.

This got lost in the quoting mess. Can you reproduce with 5.0?
-- 
Michal Hocko
SUSE Labs

Re: [External] Re: vmscan: Reclaim unevictable pages

[Pankaj Suryawanshi]

________________________________________
From: Michal Hocko <mhocko@kernel.org>
Sent: 26 March 2019 15:06
To: Pankaj Suryawanshi
Cc: Kirill Tkhai; Vlastimil Babka; aneesh.kumar@linux.ibm.com; linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com
Subject: Re: [External] Re: vmscan: Reclaim unevictable pages

On Tue 26-03-19 09:16:11, Pankaj Suryawanshi wrote:
>
> ________________________________________
> From: Michal Hocko <mhocko@kernel.org>
> Sent: 26 March 2019 14:31
> To: Pankaj Suryawanshi
> Cc: Kirill Tkhai; Vlastimil Babka; aneesh.kumar@linux.ibm.com; linux-kernel@vger.kernel.org; minchan@kernel.org; linux-mm@kvack.org; khandual@linux.vnet.ibm.com
> Subject: Re: [External] Re: vmscan: Reclaim unevictable pages
>
> [You were asked to use a reasonable quoting several times. This is
> really annoying because it turns the email thread into a complete mess]
>
> [Already fix the email client, but dont know the reason for quoting Maybe account issue.]

You clearly haven't

> As i said earlier, i am using vanilla kernel 4.14.65.

This got lost in the quoting mess. Can you reproduce with 5.0?
Actually i am using android pie-9.0, can i replace kernel 4.14.65 to 5.0 ?
--
Michal Hocko
SUSE Labs
************************************************************************************************************************************************************* eInfochips Business Disclaimer: This e-mail message and all attachments transmitted with it are intended solely for the use of the addressee and may contain legally privileged and confidential information. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, copying, or other use of this message or its attachments is strictly prohibited. If you have received this message in error, please notify the sender immediately by replying to this message and please delete it from your computer. Any views expressed in this message are those of the individual sender unless otherwise stated. Company has taken enough precautions to prevent the spread of viruses. However the company accepts no liability for any damage caused by any virus transmitted by this email. *************************************************************************************************************************************************************