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

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Message-ID: <20081205133925.GA10004@balbir.in.ibm.com>
Date:	Fri, 5 Dec 2008 19:09:26 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Li Zefan <lizf@...fujitsu.com>, Paul Menage <menage@...gle.com>
Subject: Re: [RFC][PATCH -mmotm 1/4] memcg: don't trigger oom at page
	migration

* Daisuke Nishimura <nishimura@....nes.nec.co.jp> [2008-12-05 21:23:04]:

> 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@....nes.nec.co.jp>
> ---
>  mm/memcontrol.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 4dbce1d..50ee1be 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1330,7 +1330,7 @@ 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;
>

Seems reasonable to me. A comment indicating or adding a noreclaim
wrapper around __mem_cgroup_try_charge to indicate that no reclaim
will take place will be nice.

Acked-by: Balbir Singh <balbir@...ux.vnet.ibm.com> 

-- 
	Balbir
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