[RFC][PATCH -mmotm 0/2] misc patches for memory cgroup hierarchy

[RFC][PATCH -mmotm 0/2] misc patches for memory cgroup hierarchy

[Daisuke Nishimura]

Hi.

I'm writing some patches for memory cgroup hierarchy.

I think KAMEZAWA-san's cgroup-id patches are the most important pathes now,
but I post these patches as RFC before going further.

Patch descriptions:
- [1/2] take account of memsw
    mem_cgroup_hierarchical_reclaim checks only mem->res now.
    It should also check mem->memsw when do_swap_account.
- [2/2] avoid oom
    In previous implementation, mem_cgroup_try_charge checked the return
    value of mem_cgroup_try_to_free_pages, and just retried if some pages
    had been reclaimed.
    But now, try_charge(and mem_cgroup_hierarchical_reclaim called from it)
    only checks whether the usage is less than the limit.
    I see oom easily in some tests which didn't cause oom before.

Both patches are for memory-cgroup-hierarchical-reclaim-v4 patch series.

My current plan for memory cgroup hierarchy:
- If hierarchy is enabled, limit of child should not exceed that of parent.
- Change other calls for mem_cgroup_try_to_free_page() to
  mem_cgroup_hierarchical_reclaim() if possible.


Thanks,
Daisuke Nishimura.

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[RFC][PATCH -mmotm 1/2] take account of memsw

[Daisuke Nishimura]

mem_cgroup_hierarchical_reclaim checks only mem->res now.
It should also check mem->memsw when do_swap_account.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
---
 mm/memcontrol.c |   17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 20e1d90..e7806fc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -567,6 +567,19 @@ done:
 	return ret;
 }
 
+static int mem_cgroup_check_under_limit(struct mem_cgroup *mem)
+{
+	if (do_swap_account) {
+		if (res_counter_check_under_limit(&mem->res) &&
+		    res_counter_check_under_limit(&mem->memsw))
+			return 1;
+	} else
+		if (res_counter_check_under_limit(&mem->res))
+			return 1;
+
+	return 0;
+}
+
 /*
  * Dance down the hierarchy if needed to reclaim memory. We remember the
  * last child we reclaimed from, so that we don't end up penalizing
@@ -588,7 +601,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
 	 * have left.
 	 */
 	ret = try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap);
-	if (res_counter_check_under_limit(&root_mem->res))
+	if (mem_cgroup_check_under_limit(root_mem))
 		return 0;
 
 	next_mem = mem_cgroup_get_first_node(root_mem);
@@ -602,7 +615,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
 			continue;
 		}
 		ret = try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap);
-		if (res_counter_check_under_limit(&root_mem->res))
+		if (mem_cgroup_check_under_limit(root_mem))
 			return 0;
 		cgroup_lock();
 		next_mem = mem_cgroup_get_next_node(next_mem, root_mem);

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[RFC][PATCH -mmotm 2/2] avoid oom

[Daisuke Nishimura]

In previous implementation, mem_cgroup_try_charge checked the return
value of mem_cgroup_try_to_free_pages, and just retried if some pages
had been reclaimed.
But now, try_charge(and mem_cgroup_hierarchical_reclaim called from it)
only checks whether the usage is less than the limit.
I see oom easily in some tests which didn't cause oom before.

This patch tries to change the behavior as before.

I've tested this patch with only one (except root) mem cgroup directory,
and a mem cgroup directory(use_hierarchy=1) which has 4 children with running
test programs on itself and each children's directories.

Of course, even after this patch is applied, oom happens if trying to use
too much memory.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
---

 mm/memcontrol.c |   19 ++++++++++++-------
 1 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e7806fc..ab134b7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -592,6 +592,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
 {
 	struct mem_cgroup *next_mem;
 	int ret = 0;
+	int child = 0;
 
 	/*
 	 * Reclaim unconditionally and don't check for return value.
@@ -600,9 +601,9 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
 	 * but there might be left over accounting, even after children
 	 * have left.
 	 */
-	ret = try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap);
+	ret += try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap);
 	if (mem_cgroup_check_under_limit(root_mem))
-		return 0;
+		return 1;	/* indicate success of reclaim */
 
 	next_mem = mem_cgroup_get_first_node(root_mem);
 
@@ -614,14 +615,17 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
 			cgroup_unlock();
 			continue;
 		}
-		ret = try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap);
+		child++;
+		ret += try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap);
 		if (mem_cgroup_check_under_limit(root_mem))
-			return 0;
+			return 1;	/* indicate success of reclaim */
 		cgroup_lock();
 		next_mem = mem_cgroup_get_next_node(next_mem, root_mem);
 		cgroup_unlock();
 	}
-	return ret;
+
+	/* reclaimed at least one page on average from root and each child */
+	return ret > child;
 }
 
 /*
@@ -684,8 +688,9 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
 		if (!(gfp_mask & __GFP_WAIT))
 			goto nomem;
 
-		ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, gfp_mask,
-							noswap);
+		if (mem_cgroup_hierarchical_reclaim(mem_over_limit, gfp_mask,
+							noswap))
+			continue;
 
 		/*
 		 * try_to_free_mem_cgroup_pages() might not give us a full

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Re: [RFC][PATCH -mmotm 0/2] misc patches for memory cgroup hierarchy

[KAMEZAWA Hiroyuki]

On Fri, 28 Nov 2008 18:02:52 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> Hi.
> 
> I'm writing some patches for memory cgroup hierarchy.
> 
> I think KAMEZAWA-san's cgroup-id patches are the most important pathes now,
> but I post these patches as RFC before going further.
> 
Don't wait me ;) I'll rebase mine.


> Patch descriptions:
> - [1/2] take account of memsw
>     mem_cgroup_hierarchical_reclaim checks only mem->res now.
>     It should also check mem->memsw when do_swap_account.
> - [2/2] avoid oom
>     In previous implementation, mem_cgroup_try_charge checked the return
>     value of mem_cgroup_try_to_free_pages, and just retried if some pages
>     had been reclaimed.
>     But now, try_charge(and mem_cgroup_hierarchical_reclaim called from it)
>     only checks whether the usage is less than the limit.
>     I see oom easily in some tests which didn't cause oom before.
> 
> Both patches are for memory-cgroup-hierarchical-reclaim-v4 patch series.
> 
> My current plan for memory cgroup hierarchy:
> - If hierarchy is enabled, limit of child should not exceed that of parent.
 limit of a child or
 limit of sum of children ?

> - Change other calls for mem_cgroup_try_to_free_page() to
>   mem_cgroup_hierarchical_reclaim() if possible.
> 
 maybe makes sense.

Thanks,
-Kame

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Re: [RFC][PATCH -mmotm 1/2] take account of memsw

[KAMEZAWA Hiroyuki]

On Fri, 28 Nov 2008 18:07:37 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> mem_cgroup_hierarchical_reclaim checks only mem->res now.
> It should also check mem->memsw when do_swap_account.
> 
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

make sense

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

> ---
>  mm/memcontrol.c |   17 +++++++++++++++--
>  1 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 20e1d90..e7806fc 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -567,6 +567,19 @@ done:
>  	return ret;
>  }
>  
> +static int mem_cgroup_check_under_limit(struct mem_cgroup *mem)
> +{
> +	if (do_swap_account) {
> +		if (res_counter_check_under_limit(&mem->res) &&
> +		    res_counter_check_under_limit(&mem->memsw))
> +			return 1;
> +	} else
> +		if (res_counter_check_under_limit(&mem->res))
> +			return 1;
> +
> +	return 0;
> +}
> +
>  /*
>   * Dance down the hierarchy if needed to reclaim memory. We remember the
>   * last child we reclaimed from, so that we don't end up penalizing
> @@ -588,7 +601,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
>  	 * have left.
>  	 */
>  	ret = try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap);
> -	if (res_counter_check_under_limit(&root_mem->res))
> +	if (mem_cgroup_check_under_limit(root_mem))
>  		return 0;
>  
>  	next_mem = mem_cgroup_get_first_node(root_mem);
> @@ -602,7 +615,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
>  			continue;
>  		}
>  		ret = try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap);
> -		if (res_counter_check_under_limit(&root_mem->res))
> +		if (mem_cgroup_check_under_limit(root_mem))
>  			return 0;
>  		cgroup_lock();
>  		next_mem = mem_cgroup_get_next_node(next_mem, root_mem);
> 

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Re: [RFC][PATCH -mmotm 2/2] avoid oom

[KAMEZAWA Hiroyuki]

On Fri, 28 Nov 2008 18:09:37 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> In previous implementation, mem_cgroup_try_charge checked the return
> value of mem_cgroup_try_to_free_pages, and just retried if some pages
> had been reclaimed.
> But now, try_charge(and mem_cgroup_hierarchical_reclaim called from it)
> only checks whether the usage is less than the limit.
> I see oom easily in some tests which didn't cause oom before.
> 
> This patch tries to change the behavior as before.
> 
> I've tested this patch with only one (except root) mem cgroup directory,
> and a mem cgroup directory(use_hierarchy=1) which has 4 children with running
> test programs on itself and each children's directories.
> 
> Of course, even after this patch is applied, oom happens if trying to use
> too much memory.
> 
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> ---
> 
>  mm/memcontrol.c |   19 ++++++++++++-------
>  1 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e7806fc..ab134b7 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -592,6 +592,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
>  {
>  	struct mem_cgroup *next_mem;
>  	int ret = 0;
> +	int child = 0;
>  
>  	/*
>  	 * Reclaim unconditionally and don't check for return value.
> @@ -600,9 +601,9 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
>  	 * but there might be left over accounting, even after children
>  	 * have left.
>  	 */
> -	ret = try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap);
> +	ret += try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap);
>  	if (mem_cgroup_check_under_limit(root_mem))
> -		return 0;
> +		return 1;	/* indicate success of reclaim */
>  
>  	next_mem = mem_cgroup_get_first_node(root_mem);
>  
> @@ -614,14 +615,17 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
>  			cgroup_unlock();
>  			continue;
>  		}
> -		ret = try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap);
> +		child++;
> +		ret += try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap);
>  		if (mem_cgroup_check_under_limit(root_mem))
> -			return 0;
> +			return 1;	/* indicate success of reclaim */
>  		cgroup_lock();
>  		next_mem = mem_cgroup_get_next_node(next_mem, root_mem);
>  		cgroup_unlock();
>  	}
> -	return ret;
> +
> +	/* reclaimed at least one page on average from root and each child */
> +	return ret > child;
>  }
>  
I can't understand why this heuristic...

just (ret != 0) is ?

Thanks,
-Kame



>  /*
> @@ -684,8 +688,9 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
>  		if (!(gfp_mask & __GFP_WAIT))
>  			goto nomem;
>  
> -		ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, gfp_mask,
> -							noswap);
> +		if (mem_cgroup_hierarchical_reclaim(mem_over_limit, gfp_mask,
> +							noswap))
> +			continue;
>  
>  		/*
>  		 * try_to_free_mem_cgroup_pages() might not give us a full
> 

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Re: [RFC][PATCH -mmotm 0/2] misc patches for memory cgroup hierarchy

[Daisuke Nishimura]

On Fri, 28 Nov 2008 19:49:38 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> On Fri, 28 Nov 2008 18:02:52 +0900
> Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> 
> > Hi.
> > 
> > I'm writing some patches for memory cgroup hierarchy.
> > 
> > I think KAMEZAWA-san's cgroup-id patches are the most important pathes now,
> > but I post these patches as RFC before going further.
> > 
> Don't wait me ;) I'll rebase mine.
> 
I see :)

> 
> > Patch descriptions:
> > - [1/2] take account of memsw
> >     mem_cgroup_hierarchical_reclaim checks only mem->res now.
> >     It should also check mem->memsw when do_swap_account.
> > - [2/2] avoid oom
> >     In previous implementation, mem_cgroup_try_charge checked the return
> >     value of mem_cgroup_try_to_free_pages, and just retried if some pages
> >     had been reclaimed.
> >     But now, try_charge(and mem_cgroup_hierarchical_reclaim called from it)
> >     only checks whether the usage is less than the limit.
> >     I see oom easily in some tests which didn't cause oom before.
> > 
> > Both patches are for memory-cgroup-hierarchical-reclaim-v4 patch series.
> > 
> > My current plan for memory cgroup hierarchy:
> > - If hierarchy is enabled, limit of child should not exceed that of parent.
>  limit of a child or
>  limit of sum of children ?
> 
I'm sorry for my poor explanation.
I meant *max* of limits of children.

I think setting limit like

	group A (limit=1G)
		group A0 (limit=500M)
		group A1 (limit=800M)

is not wrong itself.


Thanks,
Daisuke Nishimura.

> > - Change other calls for mem_cgroup_try_to_free_page() to
> >   mem_cgroup_hierarchical_reclaim() if possible.
> > 
>  maybe makes sense.
> 
> Thanks,
> -Kame
> 
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Re: [RFC][PATCH -mmotm 2/2] avoid oom

[Daisuke Nishimura]

On Fri, 28 Nov 2008 19:59:53 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> On Fri, 28 Nov 2008 18:09:37 +0900
> Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> 
> > In previous implementation, mem_cgroup_try_charge checked the return
> > value of mem_cgroup_try_to_free_pages, and just retried if some pages
> > had been reclaimed.
> > But now, try_charge(and mem_cgroup_hierarchical_reclaim called from it)
> > only checks whether the usage is less than the limit.
> > I see oom easily in some tests which didn't cause oom before.
> > 
> > This patch tries to change the behavior as before.
> > 
> > I've tested this patch with only one (except root) mem cgroup directory,
> > and a mem cgroup directory(use_hierarchy=1) which has 4 children with running
> > test programs on itself and each children's directories.
> > 
> > Of course, even after this patch is applied, oom happens if trying to use
> > too much memory.
> > 
> > Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> > ---
> > 
> >  mm/memcontrol.c |   19 ++++++++++++-------
> >  1 files changed, 12 insertions(+), 7 deletions(-)
> > 
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index e7806fc..ab134b7 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -592,6 +592,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
> >  {
> >  	struct mem_cgroup *next_mem;
> >  	int ret = 0;
> > +	int child = 0;
> >  
> >  	/*
> >  	 * Reclaim unconditionally and don't check for return value.
> > @@ -600,9 +601,9 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
> >  	 * but there might be left over accounting, even after children
> >  	 * have left.
> >  	 */
> > -	ret = try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap);
> > +	ret += try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap);
> >  	if (mem_cgroup_check_under_limit(root_mem))
> > -		return 0;
> > +		return 1;	/* indicate success of reclaim */
> >  
> >  	next_mem = mem_cgroup_get_first_node(root_mem);
> >  
> > @@ -614,14 +615,17 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
> >  			cgroup_unlock();
> >  			continue;
> >  		}
> > -		ret = try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap);
> > +		child++;
> > +		ret += try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap);
> >  		if (mem_cgroup_check_under_limit(root_mem))
> > -			return 0;
> > +			return 1;	/* indicate success of reclaim */
> >  		cgroup_lock();
> >  		next_mem = mem_cgroup_get_next_node(next_mem, root_mem);
> >  		cgroup_unlock();
> >  	}
> > -	return ret;
> > +
> > +	/* reclaimed at least one page on average from root and each child */
> > +	return ret > child;
> >  }
> >  
> I can't understand why this heuristic...
> 
> just (ret != 0) is ?
> 
I also thought the same thing first.

I'm worrying about the case there are many and many children.
IMHO, this function rarely fails in such cases(just because there
are many candidates to reclaim from. Ah.. I should check at least
each memcgroup has charges), so I thought it would be better
to take account of the number of children, to prevent a long software
stuck at infinite loop at __mem_cgroup_try_charge.

Actually, I tested "return ret" version in my test (4 children) too,
and I didn't see a big difference(it seemed that in "return ret" version
it took a bit long time to cause oom, but I've not confirmed it in detail).

I must consider more.


Thanks,
Daisuke Nishimura.

> Thanks,
> -Kame
> 
> 
> 
> >  /*
> > @@ -684,8 +688,9 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
> >  		if (!(gfp_mask & __GFP_WAIT))
> >  			goto nomem;
> >  
> > -		ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, gfp_mask,
> > -							noswap);
> > +		if (mem_cgroup_hierarchical_reclaim(mem_over_limit, gfp_mask,
> > +							noswap))
> > +			continue;
> >  
> >  		/*
> >  		 * try_to_free_mem_cgroup_pages() might not give us a full
> > 
> 
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Re: [RFC][PATCH -mmotm 0/2] misc patches for memory cgroup hierarchy

[Balbir Singh]

* Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> [2008-11-28 18:02:52]:

> Hi.
> 
> I'm writing some patches for memory cgroup hierarchy.
> 
> I think KAMEZAWA-san's cgroup-id patches are the most important pathes now,
> but I post these patches as RFC before going further.
> 
> Patch descriptions:
> - [1/2] take account of memsw
>     mem_cgroup_hierarchical_reclaim checks only mem->res now.
>     It should also check mem->memsw when do_swap_account.
> - [2/2] avoid oom
>     In previous implementation, mem_cgroup_try_charge checked the return
>     value of mem_cgroup_try_to_free_pages, and just retried if some pages
>     had been reclaimed.
>     But now, try_charge(and mem_cgroup_hierarchical_reclaim called from it)
>     only checks whether the usage is less than the limit.
>     I see oom easily in some tests which didn't cause oom before.
> 
> Both patches are for memory-cgroup-hierarchical-reclaim-v4 patch series.
> 
> My current plan for memory cgroup hierarchy:
> - If hierarchy is enabled, limit of child should not exceed that of parent.
> - Change other calls for mem_cgroup_try_to_free_page() to
>   mem_cgroup_hierarchical_reclaim() if possible.
>

Thanks, Daisuke,

I am in a conference and taken a quick look. The patches seem sane,
but I've not reviewed them carefully. I'll revert back next week
 

-- 
	Balbir

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