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

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Date:	Mon, 31 Aug 2015 10:46:04 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Vladimir Davydov <vdavydov@...allels.com>
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

Hello, Vladimir.

On Mon, Aug 31, 2015 at 05:20:49PM +0300, Vladimir Davydov wrote:
...
> That being said, this is the fix at the right layer.

While this *might* be a necessary workaround for the hard limit case
right now, this is by no means the fix at the right layer.  The
expectation is that mm keeps a reasonable amount of memory available
for allocations which can't block.  These allocations may fail from
time to time depending on luck and under extreme memory pressure but
the caller should be able to depend on it as a speculative allocation
mechanism which doesn't fail willy-nilly.

Hardlimit breaking GFP_NOWAIT behavior is a bug on memcg side, not
slab or slub.

Thanks.

-- 
tejun
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