linux-kernel - Re: [patch v2] mm, memcg: do not retry precharge charges

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Message-ID: <20170114162238.GD26139@cmpxchg.org>
Date:   Sat, 14 Jan 2017 11:22:38 -0500
From:   Johannes Weiner <hannes@...xchg.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [patch v2] mm, memcg: do not retry precharge charges

On Fri, Jan 13, 2017 at 02:09:53AM -0800, David Rientjes wrote:
> When memory.move_charge_at_immigrate is enabled and precharges are
> depleted during move, mem_cgroup_move_charge_pte_range() will attempt to
> increase the size of the precharge.
> 
> Prevent precharges from ever looping by setting __GFP_NORETRY.  This was
> probably the intention of the GFP_KERNEL & ~__GFP_NORETRY, which is
> pointless as written.

The OOM killer livelock was the motivation for this patch. With that
ruled out, what's the point of this patch? Try a bit less hard to move
charges during task migration?