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

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Message-ID: <5249D26C.8020208@hp.com>
Date:	Mon, 30 Sep 2013 15:35:08 -0400
From:	Waiman Long <waiman.long@...com>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	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 09/30/2013 03:23 PM, Tim Chen wrote:
> On Mon, 2013-09-30 at 20:14 +0200, Peter Zijlstra wrote:
>> 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.
> I've tested with Waiman's qrwlock patches on top of Ingo's patches.
> It does not affect the throughput for exim and I still get
> about +11.7% throughput change (same as with Ingo's patch only).
>
> Tim
>

My qrwlock doesn't enable qrwlock by default. You have to use menuconfig 
to explicitly enable it. Have you done that when you build the test 
kernel? I am thinking of explicitly enabling it for x86 if the anon-vma 
lock is converted back to a rwlock.

-Longman
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