[PATCH] memcg: remove unnecessary thp check at page stat accounting

[PATCH] memcg: remove unnecessary thp check at page stat accounting

[KAMEZAWA Hiroyuki]

Thank you very much for reviewing previous RFC series.
This is a patch against memcg-devel and linux-next (can by applied without HUNKs).

==

Re: [PATCH] memcg: remove unnecessary thp check at page stat accounting

[Michal Hocko]

On Thu 19-01-12 16:14:45, KAMEZAWA Hiroyuki wrote:
> Thank you very much for reviewing previous RFC series.
> This is a patch against memcg-devel and linux-next (can by applied without HUNKs).
> 
> ==
> 
> From 64641b360839b029bb353fbd95f7554cc806ed05 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Date: Thu, 12 Jan 2012 16:08:33 +0900
> Subject: [PATCH] memcg: remove unnecessary thp check in mem_cgroup_update_page_stat()
> 
> commit 58b318ecf(memcg-devel)
>     memcg: make mem_cgroup_split_huge_fixup() more efficient
> removes move_lock_page_cgroup() in thp-split path.

I wouldn't refer to something which will change its commit id by its
SHA. I guess the subject is sufficient. Btw. do we really need to
mention this? Is it just to make sure that this doesn't get merged
withtout the mentioned patch?

> So, We do not have to check PageTransHuge in mem_cgroup_update_page_stat
> and fallback into the locked accounting because both move charge and thp
> split up are done with compound_lock so they cannot race. update vs.
> move is protected by the mem_cgroup_stealed sufficiently.
> 
> PageTransHuge pages shouldn't appear in this code path currently because
> we are tracking only file pages at the moment but later we are planning
> to track also other pages (e.g. mlocked ones).
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Other than that
Acked-by: Michal Hocko <mhocko@suse.cz>

> ---
>  mm/memcontrol.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 5073474..fb2dfc3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1801,7 +1801,7 @@ void mem_cgroup_update_page_stat(struct page *page,
>  	if (unlikely(!memcg || !PageCgroupUsed(pc)))
>  		goto out;
>  	/* pc->mem_cgroup is unstable ? */
> -	if (unlikely(mem_cgroup_stealed(memcg)) || PageTransHuge(page)) {
> +	if (unlikely(mem_cgroup_stealed(memcg))) {
>  		/* take a lock against to access pc->mem_cgroup */
>  		move_lock_page_cgroup(pc, &flags);
>  		need_unlock = true;
> -- 
> 1.7.4.1
> 
> 
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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Re: [PATCH] memcg: remove unnecessary thp check at page stat accounting

[KAMEZAWA Hiroyuki]

On Thu, 19 Jan 2012 10:34:10 +0100
Michal Hocko <mhocko@suse.cz> wrote:

> On Thu 19-01-12 16:14:45, KAMEZAWA Hiroyuki wrote:
> > Thank you very much for reviewing previous RFC series.
> > This is a patch against memcg-devel and linux-next (can by applied without HUNKs).
> > 
> > ==
> > 
> > From 64641b360839b029bb353fbd95f7554cc806ed05 Mon Sep 17 00:00:00 2001
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > Date: Thu, 12 Jan 2012 16:08:33 +0900
> > Subject: [PATCH] memcg: remove unnecessary thp check in mem_cgroup_update_page_stat()
> > 
> > commit 58b318ecf(memcg-devel)
> >     memcg: make mem_cgroup_split_huge_fixup() more efficient
> > removes move_lock_page_cgroup() in thp-split path.
> 
> I wouldn't refer to something which will change its commit id by its
> SHA. I guess the subject is sufficient. 

> Btw. do we really need to
> mention this? Is it just to make sure that this doesn't get merged
> withtout the mentioned patch?
> 

Hmm, ok. Yes, just informing this patch depends on that patch.




> > So, We do not have to check PageTransHuge in mem_cgroup_update_page_stat
> > and fallback into the locked accounting because both move charge and thp
> > split up are done with compound_lock so they cannot race. update vs.
> > move is protected by the mem_cgroup_stealed sufficiently.
> > 
> > PageTransHuge pages shouldn't appear in this code path currently because
> > we are tracking only file pages at the moment but later we are planning
> > to track also other pages (e.g. mlocked ones).
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Other than that
> Acked-by: Michal Hocko <mhocko@suse.cz>
> 
Thank you.

-Kame

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[PATCH v3] memcg: remove unnecessary thp check at page stat accounting

[KAMEZAWA Hiroyuki]

Updated description.
==

Re: [PATCH v3] memcg: remove unnecessary thp check at page stat accounting

[Michal Hocko]

On Fri 20-01-12 12:25:12, KAMEZAWA Hiroyuki wrote:
> Updated description.
> ==
> From a6395205d9f517af7963ff61d66efbcf1c64b2a5 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Date: Thu, 12 Jan 2012 16:08:33 +0900
> Subject: [PATCH v3] memcg: remove unnecessary check in mem_cgroup_update_page_stat()
> 
> This patch is a fix for

I would rather call it a follow up for this patch. It doesn't fixes it.

>     memcg: make mem_cgroup_split_huge_fixup() more efficient
> 
> Above patch removes move_lock_page_cgroup(). So, we do not have
> to check PageTransHuge in mem_cgroup_update_page_stat and fallback into
> the locked accounting because both move_account and thp split are done
> with compound_lock so they cannot race.
> The race between update vs. move is protected by mem_cgroup_stealed,
> 
> PageTransHuge pages shouldn't appear in this code path currently because
> we are tracking only file pages at the moment but later we are planning
> to track also other pages (e.g. mlocked ones).
> 
> Changelog:
>  - updated description.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Anyway
Acked-by: Michal Hocko <mhocko@suse.cz>

Thanks
> ---
>  mm/memcontrol.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 3dbff4d..ff24520 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1867,7 +1867,7 @@ void mem_cgroup_update_page_stat(struct page *page,
>  	if (unlikely(!memcg || !PageCgroupUsed(pc)))
>  		goto out;
>  	/* pc->mem_cgroup is unstable ? */
> -	if (unlikely(mem_cgroup_stealed(memcg)) || PageTransHuge(page)) {
> +	if (unlikely(mem_cgroup_stealed(memcg))) {
>  		/* take a lock against to access pc->mem_cgroup */
>  		move_lock_page_cgroup(pc, &flags);
>  		need_unlock = true;
> -- 
> 1.7.4.1
> 
> 
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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Re: [PATCH] memcg: remove unnecessary thp check at page stat accounting

[Ying Han]

On Wed, Jan 18, 2012 at 11:14 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
> Thank you very much for reviewing previous RFC series.
> This is a patch against memcg-devel and linux-next (can by applied without HUNKs).
>
> ==
>
> From 64641b360839b029bb353fbd95f7554cc806ed05 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Date: Thu, 12 Jan 2012 16:08:33 +0900
> Subject: [PATCH] memcg: remove unnecessary thp check in mem_cgroup_update_page_stat()
>
> commit 58b318ecf(memcg-devel)
>    memcg: make mem_cgroup_split_huge_fixup() more efficient
> removes move_lock_page_cgroup() in thp-split path.
>
> So, We do not have to check PageTransHuge in mem_cgroup_update_page_stat
> and fallback into the locked accounting because both move charge and thp
> split up are done with compound_lock so they cannot race. update vs.
> move is protected by the mem_cgroup_stealed sufficiently.

Sorry, i don't see we changed the "move charge" to "move account" ?

--Ying
>
> PageTransHuge pages shouldn't appear in this code path currently because
> we are tracking only file pages at the moment but later we are planning
> to track also other pages (e.g. mlocked ones).
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

> ---
>  mm/memcontrol.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 5073474..fb2dfc3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1801,7 +1801,7 @@ void mem_cgroup_update_page_stat(struct page *page,
>        if (unlikely(!memcg || !PageCgroupUsed(pc)))
>                goto out;
>        /* pc->mem_cgroup is unstable ? */
> -       if (unlikely(mem_cgroup_stealed(memcg)) || PageTransHuge(page)) {
> +       if (unlikely(mem_cgroup_stealed(memcg))) {
>                /* take a lock against to access pc->mem_cgroup */
>                move_lock_page_cgroup(pc, &flags);
>                need_unlock = true;
> --
> 1.7.4.1
>
>

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Re: [PATCH] memcg: remove unnecessary thp check at page stat accounting

[Johannes Weiner]

On Mon, Jan 23, 2012 at 12:11:11PM -0800, Ying Han wrote:
> On Wed, Jan 18, 2012 at 11:14 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > Thank you very much for reviewing previous RFC series.
> > This is a patch against memcg-devel and linux-next (can by applied without HUNKs).
> >
> > ==
> >
> > From 64641b360839b029bb353fbd95f7554cc806ed05 Mon Sep 17 00:00:00 2001
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > Date: Thu, 12 Jan 2012 16:08:33 +0900
> > Subject: [PATCH] memcg: remove unnecessary thp check in mem_cgroup_update_page_stat()
> >
> > commit 58b318ecf(memcg-devel)
> >    memcg: make mem_cgroup_split_huge_fixup() more efficient
> > removes move_lock_page_cgroup() in thp-split path.
> >
> > So, We do not have to check PageTransHuge in mem_cgroup_update_page_stat
> > and fallback into the locked accounting because both move charge and thp
> > split up are done with compound_lock so they cannot race. update vs.
> > move is protected by the mem_cgroup_stealed sufficiently.
> 
> Sorry, i don't see we changed the "move charge" to "move account" ?

move_account() moves charges.  IMO, it's the function that is a
misnomer and "moving charges" is less ambiguous since we account
several different things in the memory controller.

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Re: [PATCH] memcg: remove unnecessary thp check at page stat accounting

[Ying Han]

On Tue, Jan 24, 2012 at 12:41 AM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> On Mon, Jan 23, 2012 at 12:11:11PM -0800, Ying Han wrote:
>> On Wed, Jan 18, 2012 at 11:14 PM, KAMEZAWA Hiroyuki
>> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>> > Thank you very much for reviewing previous RFC series.
>> > This is a patch against memcg-devel and linux-next (can by applied without HUNKs).
>> >
>> > ==
>> >
>> > From 64641b360839b029bb353fbd95f7554cc806ed05 Mon Sep 17 00:00:00 2001
>> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>> > Date: Thu, 12 Jan 2012 16:08:33 +0900
>> > Subject: [PATCH] memcg: remove unnecessary thp check in mem_cgroup_update_page_stat()
>> >
>> > commit 58b318ecf(memcg-devel)
>> >    memcg: make mem_cgroup_split_huge_fixup() more efficient
>> > removes move_lock_page_cgroup() in thp-split path.
>> >
>> > So, We do not have to check PageTransHuge in mem_cgroup_update_page_stat
>> > and fallback into the locked accounting because both move charge and thp
>> > split up are done with compound_lock so they cannot race. update vs.
>> > move is protected by the mem_cgroup_stealed sufficiently.
>>
>> Sorry, i don't see we changed the "move charge" to "move account" ?
>
> move_account() moves charges.  IMO, it's the function that is a
> misnomer and "moving charges" is less ambiguous since we account
> several different things in the memory controller.

Hmm, that works then.

Acked-by: Ying Han<yinghan@google.com>

--Ying

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