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

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Date:	Wed, 14 May 2014 11:20:51 -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 Tue, 13 May 2014, Vladimir Davydov wrote:

> Since the "slow" and the "normal" free's can't coexist at the same time,
> we must assure all conventional free's have finished before switching
> all further free's to the "slow" mode and starting reparenting. To
> achieve that, a percpu refcounter is used. It is taken and held during
> each "normal" free. The refcounter is killed on memcg offline, and the
> cache's pages migration is initiated from the refcounter's release
> function. If we fail to take a ref on kfree, it means all "normal"
> free's have been completed and the cache is being reparented right now,
> so we should free the object using the "slow" mode.

Argh adding more code to the free path touching more cachelines in the
process.

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