linux-kernel - Re: Performance regression from switching lock to rw-sem for anon-vma tree

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

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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