linux-kernel - Re: [patch 3/3] memcg: never OOM when charging huge pages

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Message-Id: <20110128084540.3a5511ba.nishimura@mxp.nes.nec.co.jp>
Date:	Fri, 28 Jan 2011 08:45:40 +0900
From:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: [patch 3/3] memcg: never OOM when charging huge pages

On Thu, 27 Jan 2011 14:47:03 +0100
Johannes Weiner <hannes@...xchg.org> wrote:

> Huge page coverage should obviously have less priority than the
> continued execution of a process.
> 
> Never kill a process when charging it a huge page fails.  Instead,
> give up after the first failed reclaim attempt and fall back to
> regular pages.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> ---
>  mm/memcontrol.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 17c4e36..2945649 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1890,6 +1890,13 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
>  	int csize = max(CHARGE_SIZE, (unsigned long) page_size);
>  
>  	/*
> +	 * Do not OOM on huge pages.  Fall back to regular pages after
> +	 * the first failed reclaim attempt.
> +	 */
> +	if (page_size > PAGE_SIZE)
> +		oom = false;
> +
> +	/*
>  	 * Unlike gloval-vm's OOM-kill, we're not in memory shortage
>  	 * in system level. So, allow to go ahead dying process in addition to
>  	 * MEMDIE process.
> -- 
> 1.7.3.5
> 
__mem_cgroup_try_charge() has "oom" switch already, so I prefer making callers
use the switch properly by themselves.

Thanks,
Daisuke Nishimura.
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