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

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Message-ID: <alpine.DEB.1.00.0910131829170.436@chino.kir.corp.google.com>
Date:	Tue, 13 Oct 2009 18:33:06 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
cc:	Pekka Enberg <penberg@...helsinki.fi>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Mel Gorman <mel@....ul.ie>,
	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 Tue, 13 Oct 2009, Christoph Lameter wrote:

> > I ran 60-second netperf TCP_RR benchmarks with various thread counts over
> > two machines, both four quad-core Opterons.  I ran the trials ten times
> > each with both vanilla per-cpu#for-next at 9288f99 and with v6 of this
> > patchset.  The transfer rates were virtually identical showing no
> > improvement or regression with this patchset in this benchmark.
> >
> >  [ As I reported in http://marc.info/?l=linux-kernel&m=123839191416472,
> >    this benchmark continues to be the most significant regression slub has
> >    compared to slab. ]
> 
> Hmmm... Last time I ran the in kernel benchmarks this showed a reduction
> in cycle counts. Did not get to get my tests yet.
> 
> Can you also try the irqless hotpath?
> 

v6 of your patchset applied to percpu#for-next now at dec54bf "this_cpu: 
Use this_cpu_xx in trace_functions_graph.c" works fine, but when I apply 
the irqless patch from http://marc.info/?l=linux-kernel&m=125503037213262 
it hangs my netserver machine within the first 60 seconds when running 
this benchmark.  These kernels both include the fixes to kmem_cache_open() 
and dma_kmalloc_cache() you posted earlier.  I'll have to debug why that's 
happening before collecting results.
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