linux-kernel - Re: [PATCH, v2] anon_vmas: Convert the rwsem to an rwlock

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Message-ID: <20130930181411.GO15690@laptop.programming.kicks-ass.net>
Date:	Mon, 30 Sep 2013 20:14:11 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Waiman Long <Waiman.Long@...com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Alex Shi <alex.shi@...el.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Matthew R Wilcox <matthew.r.wilcox@...el.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Michel Lespinasse <walken@...gle.com>,
	Andi Kleen <andi@...stfloor.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>
Subject: Re: [PATCH, v2] anon_vmas: Convert the rwsem to an rwlock_t

On Mon, Sep 30, 2013 at 10:10:27AM -0700, Tim Chen wrote:
> Here's the exim workload data:
> 
> rwsem improvment:
> Waimain's patch:        +2.0%
> Alex+Tim's patchset:    +4.8%
> Waiman+Alex+Tim:        +5.3%
> 
> convert rwsem to rwlock_t for root anon_vma lock
> Ingo's patch		+11.7%
> 

What happens if you stuff Waiman's qrwlock patches on top of that?
admittedly and oft mentioned in this thread, our current rwlock_t is
somewhat suboptimal under a number of conditions.
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