linux-kernel - Re: [patch v2] mm, memcg: periodically schedule when emptying page list

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Date:	Mon, 2 Jun 2014 21:15:10 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, Michal Hocko <mhocko@...e.cz>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	cgroups@...r.kernel.org
Subject: Re: [patch v2] mm, memcg: periodically schedule when emptying page
 list

On Mon, Jun 02, 2014 at 05:51:25PM -0700, David Rientjes wrote:
> From: Hugh Dickins <hughd@...gle.com>
> 
> mem_cgroup_force_empty_list() can iterate a large number of pages on an lru and 
> mem_cgroup_move_parent() doesn't return an errno unless certain criteria, none 
> of which indicate that the iteration may be taking too long, is met.
> 
> We have encountered the following stack trace many times indicating
> "need_resched set for > 51000020 ns (51 ticks) without schedule", for example:
> 
> 	scheduler_tick()
> 	<timer irq>
> 	mem_cgroup_move_account+0x4d/0x1d5
> 	mem_cgroup_move_parent+0x8d/0x109
> 	mem_cgroup_reparent_charges+0x149/0x2ba
> 	mem_cgroup_css_offline+0xeb/0x11b
> 	cgroup_offline_fn+0x68/0x16b
> 	process_one_work+0x129/0x350
> 
> If this iteration is taking too long, we still need to do cond_resched() even 
> when an individual page is not busy.
> 
> [rientjes@...gle.com: changelog]
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: David Rientjes <rientjes@...gle.com>

Acked-by: Johannes Weiner <hannes@...xchg.org>
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