Date: Mon, 23 Nov 2015 11:17:54 -0500
From: Johannes Weiner <hannes@cmpxchg.org>
To: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@kernel.org>, Tejun Heo <tj@kernel.org>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] memcg: fix memory.high target
Message-ID: <20151123161754.GA13000@cmpxchg.org>
References: <1448281351-15103-1-git-send-email-vdavydov@virtuozzo.com>
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On Mon, Nov 23, 2015 at 03:22:31PM +0300, Vladimir Davydov wrote:
> When the memory.high threshold is exceeded, try_charge() schedules a
> task_work to reclaim the excess. The reclaim target is set to the number
> of pages requested by try_charge(). This is wrong, because try_charge()
> usually charges more pages than requested (batch > nr_pages) in order to
> refill per cpu stocks. As a result, a process in a cgroup can easily
> exceed memory.high significantly when doing a lot of charges w/o
> returning to userspace (e.g. reading a file in big chunks).
> 
> Fix this issue by assuring that when exceeding memory.high a process
> reclaims as many pages as were actually charged (i.e. batch).
> 
> Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>

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