[PATCH -mmotm 0/4] cleanups/fixes for memory cgroup

[PATCH -mmotm 0/4] cleanups/fixes for memory cgroup

[Daisuke Nishimura]

Hi.

These are some cleanup/bug fix patches that I have now for memory cgroup.

Patches:
  [1/4] memcg: don't trigger oom at page migration
  [2/4] memcg: remove mem_cgroup_try_charge
  [3/4] memcg: avoid deadlock caused by race between oom and cpuset_attach
  [4/4] memcg: change try_to_free_pages to hierarchical_reclaim

There is no special meaning in patch order except for 1 and 2.


Thanks,
Daisuke Nishimura.

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[PATCH -mmotm 1/4] memcg: don't trigger oom at page migration

[Daisuke Nishimura]

I think triggering OOM at mem_cgroup_prepare_migration would be just a bit
overkill.
Returning -ENOMEM would be enough for mem_cgroup_prepare_migration.
The caller would handle the case anyway.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
---
 mm/memcontrol.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a4854a7..0683459 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1331,7 +1331,7 @@ int mem_cgroup_prepare_migration(struct page *page, struct mem_cgroup **ptr)
 	unlock_page_cgroup(pc);
 
 	if (mem) {
-		ret = mem_cgroup_try_charge(NULL, GFP_KERNEL, &mem);
+		ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, &mem, false);
 		css_put(&mem->css);
 	}
 	*ptr = mem;

[PATCH -mmotm 2/4] memcg: remove mem_cgroup_try_charge

[Daisuke Nishimura]

After previous patch, mem_cgroup_try_charge is not used by anyone, so we can
remove it.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by:KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 include/linux/memcontrol.h |    8 --------
 mm/memcontrol.c            |   21 +--------------------
 2 files changed, 1 insertions(+), 28 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 8752052..74c4009 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -40,8 +40,6 @@ struct mm_struct;
 extern int mem_cgroup_newpage_charge(struct page *page, struct mm_struct *mm,
 				gfp_t gfp_mask);
 /* for swap handling */
-extern int mem_cgroup_try_charge(struct mm_struct *mm,
-		gfp_t gfp_mask, struct mem_cgroup **ptr);
 extern int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
 		struct page *page, gfp_t mask, struct mem_cgroup **ptr);
 extern void mem_cgroup_commit_charge_swapin(struct page *page,
@@ -135,12 +133,6 @@ static inline int mem_cgroup_cache_charge(struct page *page,
 	return 0;
 }
 
-static inline int mem_cgroup_try_charge(struct mm_struct *mm,
-			gfp_t gfp_mask, struct mem_cgroup **ptr)
-{
-	return 0;
-}
-
 static inline int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
 		struct page *page, gfp_t gfp_mask, struct mem_cgroup **ptr)
 {
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0683459..9877b03 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -809,27 +809,8 @@ nomem:
 	return -ENOMEM;
 }
 
-/**
- * mem_cgroup_try_charge - get charge of PAGE_SIZE.
- * @mm: an mm_struct which is charged against. (when *memcg is NULL)
- * @gfp_mask: gfp_mask for reclaim.
- * @memcg: a pointer to memory cgroup which is charged against.
- *
- * charge against memory cgroup pointed by *memcg. if *memcg == NULL, estimated
- * memory cgroup from @mm is got and stored in *memcg.
- *
- * Returns 0 if success. -ENOMEM at failure.
- * This call can invoke OOM-Killer.
- */
-
-int mem_cgroup_try_charge(struct mm_struct *mm,
-			  gfp_t mask, struct mem_cgroup **memcg)
-{
-	return __mem_cgroup_try_charge(mm, mask, memcg, true);
-}
-
 /*
- * commit a charge got by mem_cgroup_try_charge() and makes page_cgroup to be
+ * commit a charge got by __mem_cgroup_try_charge() and makes page_cgroup to be
  * USED state. If already USED, uncharge and return.
  */
 

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[PATCH -mmotm 3/4] memcg: avoid dead lock caused by race between oom and cpuset_attach

[Daisuke Nishimura]

mpol_rebind_mm(), which can be called from cpuset_attach(), does down_write(mm->mmap_sem).
This means down_write(mm->mmap_sem) can be called under cgroup_mutex.

OTOH, page fault path does down_read(mm->mmap_sem) and calls mem_cgroup_try_charge_xxx(),
which may eventually calls mem_cgroup_out_of_memory(). And mem_cgroup_out_of_memory()
calls cgroup_lock().
This means cgroup_lock() can be called under down_read(mm->mmap_sem).

If those two paths race, dead lock can happen.

This patch avoid this dead lock by:
  - remove cgroup_lock() from mem_cgroup_out_of_memory().
  - define new mutex (memcg_tasklist) and serialize mem_cgroup_move_task()
    (->attach handler of memory cgroup) and mem_cgroup_out_of_memory.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu,com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
---
 mm/memcontrol.c |    5 +++++
 mm/oom_kill.c   |    2 --
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9877b03..fec4fc3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -51,6 +51,7 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/
 #define do_swap_account		(0)
 #endif
 
+static DEFINE_MUTEX(memcg_tasklist);	/* can be hold under cgroup_mutex */
 
 /*
  * Statistics for memory cgroup.
@@ -797,7 +798,9 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
 
 		if (!nr_retries--) {
 			if (oom) {
+				mutex_lock(&memcg_tasklist);
 				mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
+				mutex_unlock(&memcg_tasklist);
 				mem_over_limit->last_oom_jiffies = jiffies;
 			}
 			goto nomem;
@@ -2173,10 +2176,12 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss,
 				struct cgroup *old_cont,
 				struct task_struct *p)
 {
+	mutex_lock(&memcg_tasklist);
 	/*
 	 * FIXME: It's better to move charges of this process from old
 	 * memcg to new memcg. But it's just on TODO-List now.
 	 */
+	mutex_unlock(&memcg_tasklist);
 }
 
 struct cgroup_subsys mem_cgroup_subsys = {
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index fd150e3..40ba050 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -429,7 +429,6 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
 	unsigned long points = 0;
 	struct task_struct *p;
 
-	cgroup_lock();
 	read_lock(&tasklist_lock);
 retry:
 	p = select_bad_process(&points, mem);
@@ -444,7 +443,6 @@ retry:
 		goto retry;
 out:
 	read_unlock(&tasklist_lock);
-	cgroup_unlock();
 }
 #endif
 

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[PATCH -mmotm 4/4] memcg: change try_to_free_pages to hierarchical_reclaim

[Daisuke Nishimura]

mem_cgroup_hierarchicl_reclaim() works properly even when !use_hierarchy now
(by memcg-hierarchy-avoid-unnecessary-reclaim.patch), so, instead of
try_to_free_mem_cgroup_pages(), it should be used in many cases.

The only exception is force_empty. The group has no children in this case.


Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
---
 mm/memcontrol.c |   12 ++++--------
 1 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index fec4fc3..b2b5c57 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1400,8 +1400,7 @@ int mem_cgroup_shrink_usage(struct mm_struct *mm, gfp_t gfp_mask)
 	rcu_read_unlock();
 
 	do {
-		progress = try_to_free_mem_cgroup_pages(mem, gfp_mask, true,
-							get_swappiness(mem));
+		progress = mem_cgroup_hierarchical_reclaim(mem, gfp_mask, true);
 		progress += mem_cgroup_check_under_limit(mem);
 	} while (!progress && --retry);
 
@@ -1468,10 +1467,8 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
 		if (!ret)
 			break;
 
-		progress = try_to_free_mem_cgroup_pages(memcg,
-							GFP_KERNEL,
-							false,
-							get_swappiness(memcg));
+		progress = mem_cgroup_hierarchical_reclaim(memcg, GFP_KERNEL,
+							   false);
   		if (!progress)			retry_count--;
 	}
 
@@ -1515,8 +1512,7 @@ int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
 			break;
 
 		oldusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
-		try_to_free_mem_cgroup_pages(memcg, GFP_KERNEL, true,
-					     get_swappiness(memcg));
+		mem_cgroup_hierarchical_reclaim(memcg, GFP_KERNEL, true);
 		curusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
 		if (curusage >= oldusage)
 			retry_count--;

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Re: [PATCH -mmotm 3/4] memcg: avoid dead lock caused by race between oom and cpuset_attach

[Daisuke Nishimura]

On Mon, 8 Dec 2008 11:05:11 +0900, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> mpol_rebind_mm(), which can be called from cpuset_attach(), does down_write(mm->mmap_sem).
> This means down_write(mm->mmap_sem) can be called under cgroup_mutex.
> 
> OTOH, page fault path does down_read(mm->mmap_sem) and calls mem_cgroup_try_charge_xxx(),
> which may eventually calls mem_cgroup_out_of_memory(). And mem_cgroup_out_of_memory()
> calls cgroup_lock().
> This means cgroup_lock() can be called under down_read(mm->mmap_sem).
> 
> If those two paths race, dead lock can happen.
> 
> This patch avoid this dead lock by:
>   - remove cgroup_lock() from mem_cgroup_out_of_memory().
>   - define new mutex (memcg_tasklist) and serialize mem_cgroup_move_task()
>     (->attach handler of memory cgroup) and mem_cgroup_out_of_memory.
> 
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu,com>
Ooops, Kamezawa-san's address was invalid...

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>


Sorry.
Daisuke Nishimura.

> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
> ---
>  mm/memcontrol.c |    5 +++++
>  mm/oom_kill.c   |    2 --
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 9877b03..fec4fc3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -51,6 +51,7 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/
>  #define do_swap_account		(0)
>  #endif
>  
> +static DEFINE_MUTEX(memcg_tasklist);	/* can be hold under cgroup_mutex */
>  
>  /*
>   * Statistics for memory cgroup.
> @@ -797,7 +798,9 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
>  
>  		if (!nr_retries--) {
>  			if (oom) {
> +				mutex_lock(&memcg_tasklist);
>  				mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
> +				mutex_unlock(&memcg_tasklist);
>  				mem_over_limit->last_oom_jiffies = jiffies;
>  			}
>  			goto nomem;
> @@ -2173,10 +2176,12 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss,
>  				struct cgroup *old_cont,
>  				struct task_struct *p)
>  {
> +	mutex_lock(&memcg_tasklist);
>  	/*
>  	 * FIXME: It's better to move charges of this process from old
>  	 * memcg to new memcg. But it's just on TODO-List now.
>  	 */
> +	mutex_unlock(&memcg_tasklist);
>  }
>  
>  struct cgroup_subsys mem_cgroup_subsys = {
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index fd150e3..40ba050 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -429,7 +429,6 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
>  	unsigned long points = 0;
>  	struct task_struct *p;
>  
> -	cgroup_lock();
>  	read_lock(&tasklist_lock);
>  retry:
>  	p = select_bad_process(&points, mem);
> @@ -444,7 +443,6 @@ retry:
>  		goto retry;
>  out:
>  	read_unlock(&tasklist_lock);
> -	cgroup_unlock();
>  }
>  #endif
>  

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Re: [PATCH -mmotm 3/4] memcg: avoid dead lock caused by race between oom and cpuset_attach

[Paul Menage]

On Sun, Dec 7, 2008 at 6:05 PM, Daisuke Nishimura
<nishimura@mxp.nes.nec.co.jp> wrote:
> mpol_rebind_mm(), which can be called from cpuset_attach(), does down_write(mm->mmap_sem).
> This means down_write(mm->mmap_sem) can be called under cgroup_mutex.
>
> OTOH, page fault path does down_read(mm->mmap_sem) and calls mem_cgroup_try_charge_xxx(),
> which may eventually calls mem_cgroup_out_of_memory(). And mem_cgroup_out_of_memory()
> calls cgroup_lock().
> This means cgroup_lock() can be called under down_read(mm->mmap_sem).

We should probably try to get cgroup_lock() out of the cpuset code
that calls mpol_rebind_mm() as well.

Paul

>
> If those two paths race, dead lock can happen.
>
> This patch avoid this dead lock by:
>  - remove cgroup_lock() from mem_cgroup_out_of_memory().
>  - define new mutex (memcg_tasklist) and serialize mem_cgroup_move_task()
>    (->attach handler of memory cgroup) and mem_cgroup_out_of_memory.
>
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu,com>
> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
> ---
>  mm/memcontrol.c |    5 +++++
>  mm/oom_kill.c   |    2 --
>  2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 9877b03..fec4fc3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -51,6 +51,7 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/
>  #define do_swap_account                (0)
>  #endif
>
> +static DEFINE_MUTEX(memcg_tasklist);   /* can be hold under cgroup_mutex */
>
>  /*
>  * Statistics for memory cgroup.
> @@ -797,7 +798,9 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
>
>                if (!nr_retries--) {
>                        if (oom) {
> +                               mutex_lock(&memcg_tasklist);
>                                mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
> +                               mutex_unlock(&memcg_tasklist);
>                                mem_over_limit->last_oom_jiffies = jiffies;
>                        }
>                        goto nomem;
> @@ -2173,10 +2176,12 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss,
>                                struct cgroup *old_cont,
>                                struct task_struct *p)
>  {
> +       mutex_lock(&memcg_tasklist);
>        /*
>         * FIXME: It's better to move charges of this process from old
>         * memcg to new memcg. But it's just on TODO-List now.
>         */
> +       mutex_unlock(&memcg_tasklist);
>  }
>
>  struct cgroup_subsys mem_cgroup_subsys = {
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index fd150e3..40ba050 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -429,7 +429,6 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
>        unsigned long points = 0;
>        struct task_struct *p;
>
> -       cgroup_lock();
>        read_lock(&tasklist_lock);
>  retry:
>        p = select_bad_process(&points, mem);
> @@ -444,7 +443,6 @@ retry:
>                goto retry;
>  out:
>        read_unlock(&tasklist_lock);
> -       cgroup_unlock();
>  }
>  #endif
>
>

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