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

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Message-ID: <CANN689GtHw6dDeMd+2fuUz_dv_Z44XndVj2u-TNy70qkZWkpDw@mail.gmail.com>
Date:	Fri, 14 Jun 2013 15:47:13 -0700
From:	Michel Lespinasse <walken@...gle.com>
To:	Davidlohr Bueso <davidlohr.bueso@...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>, "Shi, Alex" <alex.shi@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Wilcox, Matthew R" <matthew.r.wilcox@...el.com>,
	Dave Hansen <dave.hansen@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>
Subject: Re: Performance regression from switching lock to rw-sem for anon-vma tree

On Fri, Jun 14, 2013 at 3:31 PM, Davidlohr Bueso <davidlohr.bueso@...com> wrote:
> A few ideas that come to mind are avoiding taking the ->wait_lock and
> avoid dealing with waiters when doing the optimistic spinning (just like
> mutexes do).
>
> I agree that we should first deal with the optimistic spinning before
> adding the MCS complexity.

Maybe it would be worth disabling the MCS patch in mutex and comparing
that to the rwsem patches ? Just to make sure the rwsem performance
delta isn't related to that.

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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