linux-kernel - Re: [PATCH 0/2] Fix memcg/memory.high in case kmem accounting is enabled

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Message-ID: <20150831143007.GA13814@esperanza>
Date:	Mon, 31 Aug 2015 17:30:08 +0300
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Michal Hocko <mhocko@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2] Fix memcg/memory.high in case kmem accounting is
 enabled

On Mon, Aug 31, 2015 at 09:43:35AM -0400, Tejun Heo wrote:
> On Mon, Aug 31, 2015 at 03:24:15PM +0200, Michal Hocko wrote:
> > Right but isn't that what the caller explicitly asked for? Why should we
> > ignore that for kmem accounting? It seems like a fix at a wrong layer to
> > me. Either we should start failing GFP_NOWAIT charges when we are above
> > high wmark or deploy an additional catchup mechanism as suggested by
> > Tejun. I like the later more because it allows to better handle GFP_NOFS
> > requests as well and there are many sources of these from kmem paths.
> 
> Yeah, this is beginning to look like we're trying to solve the problem
> at the wrong layer.  slab/slub or whatever else should be able to use
> GFP_NOWAIT in whatever frequency they want for speculative
> allocations.

slab/slub can issue alloc_pages() any time with any flags they want and
it won't be accounted to memcg, because kmem is accounted at slab/slub
layer, not in buddy.

Thanks,
Vladimir
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