linux-kernel - Re: [PATCH RFC 3/3] slub: reparent memcg caches' slabs on memcg offline

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Date:	Wed, 21 May 2014 09:45:54 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Vladimir Davydov <vdavydov@...allels.com>
cc:	hannes@...xchg.org, mhocko@...e.cz, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH RFC 3/3] slub: reparent memcg caches' slabs on memcg
 offline

On Wed, 21 May 2014, Vladimir Davydov wrote:

> Seems I've found a better way to avoid this race, which does not involve
> messing up free hot paths. The idea is to explicitly zap each per-cpu
> partial list by setting it pointing to an invalid ptr. Since
> put_cpu_partial(), which is called from __slab_free(), uses atomic
> cmpxchg for adding a new partial slab to a per cpu partial list, it is
> enough to add a check if partials are zapped there and bail out if so.
>
> The patch doing the trick is attached. Could you please take a look at
> it once time permit?

Well if you set s->cpu_partial = 0 then the slab should not be added to
the partial lists. Ok its put on there temporarily but then immediately
moved to the node partial list in put_cpu_partial().

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