Date: Tue, 29 May 2012 09:19:02 -0500 (CDT)
From: Christoph Lameter <cl@linux.com>
To: Glauber Costa <glommer@parallels.com>
cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org,
        kamezawa.hiroyu@jp.fujitsu.com, Tejun Heo <tj@kernel.org>,
        Li Zefan <lizefan@huawei.com>, Greg Thelen <gthelen@google.com>,
        Suleiman Souhlal <suleiman@google.com>, Michal Hocko <mhocko@suse.cz>,
        Johannes Weiner <hannes@cmpxchg.org>, devel@openvz.org,
        David Rientjes <rientjes@google.com>
Subject: Re: [PATCH v3 05/28] memcg: Reclaim when more than one page
 needed.
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References: <1337951028-3427-1-git-send-email-glommer@parallels.com> <1337951028-3427-6-git-send-email-glommer@parallels.com>
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On Fri, 25 May 2012, Glauber Costa wrote:

> From: Suleiman Souhlal <ssouhlal@FreeBSD.org>
>
> mem_cgroup_do_charge() was written before slab accounting, and expects
> three cases: being called for 1 page, being called for a stock of 32 pages,
> or being called for a hugepage.  If we call for 2 pages (and several slabs
> used in process creation are such, at least with the debug options I had),
> it assumed it's being called for stock and just retried without reclaiming.

Slab pages are allocated up to order 3 (PAGE_ALLOC_COSTLY_ORDER). That is
8 pages.

>  	 * unlikely to succeed so close to the limit, and we fall back
>  	 * to regular pages anyway in case of failure.
>  	 */
> -	if (nr_pages == 1 && ret)
> +	if (nr_pages <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER) && ret) {
> +		cond_resched();
>  		return CHARGE_RETRY;
> +	}
>
>  	/*
>  	 * At task move, charge accounts can be doubly counted. So, it's

Ok. That looks correct.

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