linux-kernel - Re: [patch 2/2] fs: buffer: move allocation failure loop into the allocator

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Message-ID: <00000142be753b07-aa0e2354-6704-41f8-8e11-3c856a186af5-000000@email.amazonses.com>
Date:	Wed, 4 Dec 2013 16:33:43 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Joonsoo Kim <js1304@...il.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>, azurIt <azurit@...ox.sk>,
	Linux Memory Management List <linux-mm@...ck.org>,
	cgroups@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Christian Casteyde <casteyde.christian@...e.fr>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: [patch 2/2] fs: buffer: move allocation failure loop into the
 allocator

On Thu, 5 Dec 2013, Joonsoo Kim wrote:

> Now we have cpu partial slabs facility, so I think that slowpath isn't really
> slow. And it doesn't much increase the management overhead in the node
> partial lists, because of cpu partial slabs.

Well yes that may address some of the issues here.

> And larger frame may cause more slab_lock contention or cmpxchg contention
> if there are parallel freeings.
>
> But, I don't know which one is better. Is larger frame still better? :)

Could you run some tests to figure this one out? There are also
some situations in which we disable the per cpu partial pages though.
F.e. for low latency/realtime. I posted in kernel synthetic
benchmarks for slab a while back. That maybe something to start with.


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