linux-kernel - Re: [PATCH v3 05/28] memcg: Reclaim when more than one page needed.

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Date:	Tue, 29 May 2012 09:19:02 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Glauber Costa <glommer@...allels.com>
cc:	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	linux-mm@...ck.org, kamezawa.hiroyu@...fujitsu.com,
	Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
	Greg Thelen <gthelen@...gle.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>, devel@...nvz.org,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH v3 05/28] memcg: Reclaim when more than one page
 needed.

On Fri, 25 May 2012, Glauber Costa wrote:

> From: Suleiman Souhlal <ssouhlal@...eBSD.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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