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Subject: Re: Performance regression from switching lock to rw-sem for
 anon-vma tree
From: Davidlohr Bueso <davidlohr.bueso@hp.com>
Date: Mon, 17 Jun 2013 16:35:20 -0700
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To: Alex Shi <alex.shi@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>, Ingo Molnar <mingo@elte.hu>, Rik van Riel <riel@redhat.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Andrea Arcangeli <aarcange@redhat.com>, Mel Gorman <mgorman@suse.de>, Andi Kleen <andi@firstfloor.org>, Andrew Morton <akpm@linux-foundation.org>, Michel Lespinasse <walken@google.com>, "Wilcox, Matthew R" <matthew.r.wilcox@intel.com>, Dave Hansen <dave.hansen@intel.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>

On Tue, 2013-06-18 at 07:20 +0800, Alex Shi wrote:
> On 06/18/2013 12:22 AM, Davidlohr Bueso wrote:
> > After a lot of benchmarking, I finally got the ideal results for aim7,
> > so far: this patch + optimistic spinning with preemption disabled. Just
> > like optimistic spinning, this patch by itself makes little to no
> > difference, yet combined is where we actually outperform 3.10-rc5. In
> > addition, I noticed extra throughput when disabling preemption in
> > try_optimistic_spin().
> > 
> > With i_mmap as a rwsem and these changes I could see performance
> > benefits for alltests (+14.5%), custom (+17%), disk (+11%), high_systime
> > (+5%), shared (+15%) and short (+4%), most of them after around 500
> > users, for fewer users, it made little to no difference.
> 
> A pretty good number. what's the cpu number in your machine? :)

8-socket, 80 cores (ht off)


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