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Message-Id: <20081128195953.0f69d9ea.kamezawa.hiroyu@jp.fujitsu.com>
Date: Fri, 28 Nov 2008 19:59:53 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc: LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
Pavel Emelyanov <xemul@...nvz.org>,
Li Zefan <lizf@...fujitsu.com>, Paul Menage <menage@...gle.com>
Subject: Re: [RFC][PATCH -mmotm 2/2] avoid oom
On Fri, 28 Nov 2008 18:09:37 +0900
Daisuke Nishimura <nishimura@....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@....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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