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

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Date:	Thu, 5 Dec 2013 17:44:41 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	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 Wed, Dec 04, 2013 at 04:33:43PM +0000, Christoph Lameter wrote:
> 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.

I could try. But my trial would not figure this out, since my machine has
just 4 cores which normally cannot produce heavy contention.
Anyway, could you tell me where I can find your synthetic benchmarks for slab?

Thanks.
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