[PATCH 0/2] memcg: some fixes for -rc

[PATCH 0/2] memcg: some fixes for -rc

[Daisuke Nishimura]

These are bugfix patches for memcg I've been testing for a few weeks.

They are based on -rc1, and can be applied to mmotm(2009-04-17-15-19) too.

[1/2] memcg: fix shrink_usage
[2/2] memcg: free unused swapcache at the end of page migration

Thanks,
Daisuke Nishimura.

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[PATCH 1/2] memcg: fix shrink_usage

[Daisuke Nishimura]

Current mem_cgroup_shrink_usage has two problems.

1. It doesn't call mem_cgroup_out_of_memory and doesn't update last_oom_jiffies,
   so pagefault_out_of_memory invokes global OOM.
2. Considering hierarchy, shrinking has to be done from the mem_over_limit,
   not from the memcg which the page would be charged to.

mem_cgroup_try_charge_swapin does all of these works properly,
so we use it and call cancel_charge_swapin when it succeeded.

The name of "shrink_usage" is not appropriate for this behavior,
so we change it too.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 include/linux/memcontrol.h |    4 ++--
 mm/memcontrol.c            |   33 ++++++++++++---------------------
 mm/shmem.c                 |    8 ++++++--
 3 files changed, 20 insertions(+), 25 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 18146c9..928b714 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -56,7 +56,7 @@ extern void mem_cgroup_move_lists(struct page *page,
 				  enum lru_list from, enum lru_list to);
 extern void mem_cgroup_uncharge_page(struct page *page);
 extern void mem_cgroup_uncharge_cache_page(struct page *page);
-extern int mem_cgroup_shrink_usage(struct page *page,
+extern int mem_cgroup_shmem_charge_fallback(struct page *page,
 			struct mm_struct *mm, gfp_t gfp_mask);
 
 extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
@@ -155,7 +155,7 @@ static inline void mem_cgroup_uncharge_cache_page(struct page *page)
 {
 }
 
-static inline int mem_cgroup_shrink_usage(struct page *page,
+static inline int mem_cgroup_shmem_charge_fallback(struct page *page,
 			struct mm_struct *mm, gfp_t gfp_mask)
 {
 	return 0;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2fc6d6c..619b0c1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1618,37 +1618,28 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem,
 }
 
 /*
- * A call to try to shrink memory usage under specified resource controller.
- * This is typically used for page reclaiming for shmem for reducing side
- * effect of page allocation from shmem, which is used by some mem_cgroup.
+ * A call to try to shrink memory usage on charge failure at shmem's swapin.
+ * Calling hierarchical_reclaim is not enough because we should update
+ * last_oom_jiffies to prevent pagefault_out_of_memory from invoking global OOM.
+ * Moreover considering hierarchy, we should reclaim from the mem_over_limit,
+ * not from the memcg which this page would be charged to.
+ * try_charge_swapin does all of these works properly.
  */
-int mem_cgroup_shrink_usage(struct page *page,
+int mem_cgroup_shmem_charge_fallback(struct page *page,
 			    struct mm_struct *mm,
 			    gfp_t gfp_mask)
 {
 	struct mem_cgroup *mem = NULL;
-	int progress = 0;
-	int retry = MEM_CGROUP_RECLAIM_RETRIES;
+	int ret;
 
 	if (mem_cgroup_disabled())
 		return 0;
-	if (page)
-		mem = try_get_mem_cgroup_from_swapcache(page);
-	if (!mem && mm)
-		mem = try_get_mem_cgroup_from_mm(mm);
-	if (unlikely(!mem))
-		return 0;
 
-	do {
-		progress = mem_cgroup_hierarchical_reclaim(mem,
-					gfp_mask, true, false);
-		progress += mem_cgroup_check_under_limit(mem);
-	} while (!progress && --retry);
+	ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem);
+	if (!ret)
+		mem_cgroup_cancel_charge_swapin(mem); /* it does !mem check */
 
-	css_put(&mem->css);
-	if (!retry)
-		return -ENOMEM;
-	return 0;
+	return ret;
 }
 
 static DEFINE_MUTEX(set_limit_mutex);
diff --git a/mm/shmem.c b/mm/shmem.c
index d94d2e9..2419562 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1325,8 +1325,12 @@ repeat:
 			shmem_swp_unmap(entry);
 			spin_unlock(&info->lock);
 			if (error == -ENOMEM) {
-				/* allow reclaim from this memory cgroup */
-				error = mem_cgroup_shrink_usage(swappage,
+				/*
+				 * reclaim from proper memory cgroup and
+				 * call memcg's OOM if needed.
+				 */
+				error = mem_cgroup_shmem_charge_fallback(
+								swappage,
 								current->mm,
 								gfp);
 				if (error) {

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[PATCH 2/2] memcg: free unused swapcache at the end of page migration

[Daisuke Nishimura]

Reading the comments, mem_cgroup_end_migration assumes that "newpage" is under lock_page.

And at the end of mem_cgroup_end_migration, mem_cgroup_uncharge_page cannot
uncharge the "target" if it's SwapCache even if the owner process has already
called zap_pte_range -> free_swap_and_cache.
try_to_free_swap does all necessary checks(it checks page_swapcount).

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
---
 mm/memcontrol.c |    7 +++++--
 mm/migrate.c    |    9 +++++++--
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 619b0c1..f41433c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1611,10 +1611,13 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem,
 	 * There is a case for !page_mapped(). At the start of
 	 * migration, oldpage was mapped. But now, it's zapped.
 	 * But we know *target* page is not freed/reused under us.
-	 * mem_cgroup_uncharge_page() does all necessary checks.
+	 * mem_cgroup_uncharge_page() cannot free SwapCache, so we call
+	 * try_to_free_swap(), which does all necessary checks.
 	 */
-	if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)
+	if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED && !page_mapped(target)) {
 		mem_cgroup_uncharge_page(target);
+		try_to_free_swap(target);
+	}
 }
 
 /*
diff --git a/mm/migrate.c b/mm/migrate.c
index 068655d..364edf7 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -580,7 +580,7 @@ static int move_to_new_page(struct page *newpage, struct page *page)
 	} else
 		newpage->mapping = NULL;
 
-	unlock_page(newpage);
+	/* keep lock on newpage because mem_cgroup_end_migration assumes it */
 
 	return rc;
 }
@@ -595,6 +595,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
 	int rc = 0;
 	int *result = NULL;
 	struct page *newpage = get_new_page(page, private, &result);
+	int newpage_locked = 0;
 	int rcu_locked = 0;
 	int charge = 0;
 	struct mem_cgroup *mem;
@@ -671,8 +672,10 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
 	/* Establish migration ptes or remove ptes */
 	try_to_unmap(page, 1);
 
-	if (!page_mapped(page))
+	if (!page_mapped(page)) {
 		rc = move_to_new_page(newpage, page);
+		newpage_locked = 1;
+	}
 
 	if (rc)
 		remove_migration_ptes(page, page);
@@ -683,6 +686,8 @@ uncharge:
 	if (!charge)
 		mem_cgroup_end_migration(mem, page, newpage);
 unlock:
+	if (newpage_locked)
+		unlock_page(newpage);
 	unlock_page(page);
 
 	if (rc != -EAGAIN) {

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Re: [PATCH 2/2] memcg: free unused swapcache at the end of page migration

[KAMEZAWA Hiroyuki]

On Tue, 21 Apr 2009 14:29:31 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> Reading the comments, mem_cgroup_end_migration assumes that "newpage" is under lock_page.
> 
> And at the end of mem_cgroup_end_migration, mem_cgroup_uncharge_page cannot
> uncharge the "target" if it's SwapCache even if the owner process has already
> called zap_pte_range -> free_swap_and_cache.
> try_to_free_swap does all necessary checks(it checks page_swapcount).
> 
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

Nishimura-san, I'd like to handle this issue by my own handle-stale-swapcache patch.
(I'll post it today.)

So, could you wait this patch for a while ?

Thanks,
-Kame

> ---
>  mm/memcontrol.c |    7 +++++--
>  mm/migrate.c    |    9 +++++++--
>  2 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 619b0c1..f41433c 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1611,10 +1611,13 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem,
>  	 * There is a case for !page_mapped(). At the start of
>  	 * migration, oldpage was mapped. But now, it's zapped.
>  	 * But we know *target* page is not freed/reused under us.
> -	 * mem_cgroup_uncharge_page() does all necessary checks.
> +	 * mem_cgroup_uncharge_page() cannot free SwapCache, so we call
> +	 * try_to_free_swap(), which does all necessary checks.
>  	 */
> -	if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)
> +	if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED && !page_mapped(target)) {
>  		mem_cgroup_uncharge_page(target);
> +		try_to_free_swap(target);
> +	}
>  }
>  
>  /*
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 068655d..364edf7 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -580,7 +580,7 @@ static int move_to_new_page(struct page *newpage, struct page *page)
>  	} else
>  		newpage->mapping = NULL;
>  
> -	unlock_page(newpage);
> +	/* keep lock on newpage because mem_cgroup_end_migration assumes it */
>  
>  	return rc;
>  }
> @@ -595,6 +595,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
>  	int rc = 0;
>  	int *result = NULL;
>  	struct page *newpage = get_new_page(page, private, &result);
> +	int newpage_locked = 0;
>  	int rcu_locked = 0;
>  	int charge = 0;
>  	struct mem_cgroup *mem;
> @@ -671,8 +672,10 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
>  	/* Establish migration ptes or remove ptes */
>  	try_to_unmap(page, 1);
>  
> -	if (!page_mapped(page))
> +	if (!page_mapped(page)) {
>  		rc = move_to_new_page(newpage, page);
> +		newpage_locked = 1;
> +	}
>  
>  	if (rc)
>  		remove_migration_ptes(page, page);
> @@ -683,6 +686,8 @@ uncharge:
>  	if (!charge)
>  		mem_cgroup_end_migration(mem, page, newpage);
>  unlock:
> +	if (newpage_locked)
> +		unlock_page(newpage);
>  	unlock_page(page);
>  
>  	if (rc != -EAGAIN) {
> 

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Re: [PATCH 1/2] memcg: fix shrink_usage

[KAMEZAWA Hiroyuki]

On Tue, 21 Apr 2009 14:29:18 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> Current mem_cgroup_shrink_usage has two problems.
> 
> 1. It doesn't call mem_cgroup_out_of_memory and doesn't update last_oom_jiffies,
>    so pagefault_out_of_memory invokes global OOM.
> 2. Considering hierarchy, shrinking has to be done from the mem_over_limit,
>    not from the memcg which the page would be charged to.
> 
> mem_cgroup_try_charge_swapin does all of these works properly,
> so we use it and call cancel_charge_swapin when it succeeded.
> 
> The name of "shrink_usage" is not appropriate for this behavior,
> so we change it too.
> 
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Thank you!.
-Kame

> ---
>  include/linux/memcontrol.h |    4 ++--
>  mm/memcontrol.c            |   33 ++++++++++++---------------------
>  mm/shmem.c                 |    8 ++++++--
>  3 files changed, 20 insertions(+), 25 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 18146c9..928b714 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -56,7 +56,7 @@ extern void mem_cgroup_move_lists(struct page *page,
>  				  enum lru_list from, enum lru_list to);
>  extern void mem_cgroup_uncharge_page(struct page *page);
>  extern void mem_cgroup_uncharge_cache_page(struct page *page);
> -extern int mem_cgroup_shrink_usage(struct page *page,
> +extern int mem_cgroup_shmem_charge_fallback(struct page *page,
>  			struct mm_struct *mm, gfp_t gfp_mask);
>  
>  extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
> @@ -155,7 +155,7 @@ static inline void mem_cgroup_uncharge_cache_page(struct page *page)
>  {
>  }
>  
> -static inline int mem_cgroup_shrink_usage(struct page *page,
> +static inline int mem_cgroup_shmem_charge_fallback(struct page *page,
>  			struct mm_struct *mm, gfp_t gfp_mask)
>  {
>  	return 0;
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2fc6d6c..619b0c1 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1618,37 +1618,28 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem,
>  }
>  
>  /*
> - * A call to try to shrink memory usage under specified resource controller.
> - * This is typically used for page reclaiming for shmem for reducing side
> - * effect of page allocation from shmem, which is used by some mem_cgroup.
> + * A call to try to shrink memory usage on charge failure at shmem's swapin.
> + * Calling hierarchical_reclaim is not enough because we should update
> + * last_oom_jiffies to prevent pagefault_out_of_memory from invoking global OOM.
> + * Moreover considering hierarchy, we should reclaim from the mem_over_limit,
> + * not from the memcg which this page would be charged to.
> + * try_charge_swapin does all of these works properly.
>   */
> -int mem_cgroup_shrink_usage(struct page *page,
> +int mem_cgroup_shmem_charge_fallback(struct page *page,
>  			    struct mm_struct *mm,
>  			    gfp_t gfp_mask)
>  {
>  	struct mem_cgroup *mem = NULL;
> -	int progress = 0;
> -	int retry = MEM_CGROUP_RECLAIM_RETRIES;
> +	int ret;
>  
>  	if (mem_cgroup_disabled())
>  		return 0;
> -	if (page)
> -		mem = try_get_mem_cgroup_from_swapcache(page);
> -	if (!mem && mm)
> -		mem = try_get_mem_cgroup_from_mm(mm);
> -	if (unlikely(!mem))
> -		return 0;
>  
> -	do {
> -		progress = mem_cgroup_hierarchical_reclaim(mem,
> -					gfp_mask, true, false);
> -		progress += mem_cgroup_check_under_limit(mem);
> -	} while (!progress && --retry);
> +	ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem);
> +	if (!ret)
> +		mem_cgroup_cancel_charge_swapin(mem); /* it does !mem check */
>  
> -	css_put(&mem->css);
> -	if (!retry)
> -		return -ENOMEM;
> -	return 0;
> +	return ret;
>  }
>  
>  static DEFINE_MUTEX(set_limit_mutex);
> diff --git a/mm/shmem.c b/mm/shmem.c
> index d94d2e9..2419562 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1325,8 +1325,12 @@ repeat:
>  			shmem_swp_unmap(entry);
>  			spin_unlock(&info->lock);
>  			if (error == -ENOMEM) {
> -				/* allow reclaim from this memory cgroup */
> -				error = mem_cgroup_shrink_usage(swappage,
> +				/*
> +				 * reclaim from proper memory cgroup and
> +				 * call memcg's OOM if needed.
> +				 */
> +				error = mem_cgroup_shmem_charge_fallback(
> +								swappage,
>  								current->mm,
>  								gfp);
>  				if (error) {
> 
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