linux-kernel - Re: [this_cpu_xx V6 7/7] this_cpu: slub aggressive use of this

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Message-ID: <alpine.DEB.1.00.0910161141280.21328@chino.kir.corp.google.com>
Date:	Fri, 16 Oct 2009 11:43:23 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
cc:	Mel Gorman <mel@....ul.ie>, Pekka Enberg <penberg@...helsinki.fi>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>
Subject: Re: [this_cpu_xx V6 7/7] this_cpu: slub aggressive use of this_cpu
 operations in the hotpaths

On Fri, 16 Oct 2009, Christoph Lameter wrote:

> > TCP_STREAM stresses a few specific caches:
> >
> > 		ALLOC_FASTPATH	ALLOC_SLOWPATH	FREE_FASTPATH	FREE_SLOWPATH
> > kmalloc-256	3868530		3450592		95628		7223491
> > kmalloc-1024	2440434		429		2430825		10034
> > kmalloc-4096	3860625		1036723		85571		4811779
> >
> > This demonstrates that freeing to full (or partial) slabs causes a lot of
> > pain since the fastpath normally can't be utilized and that's probably
> > beyond the scope of this patchset.
> >
> > It's also different from the cpu slab thrashing issue I identified with
> > the TCP_RR benchmark and had a patchset to somewhat improve.  The
> > criticism was the addition of an increment to a fastpath counter in struct
> > kmem_cache_cpu which could probably now be much cheaper with these
> > optimizations.
> 
> Can you redo the patch?
> 

Sure, but it would be even more inexpensive if we can figure out why the 
irqless patch is hanging my netserver machine within the first 60 seconds 
on the TCP_RR benchmark.  I guess nobody else has reproduced that yet.
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