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From: Dave Chinner <david@fromorbit.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Waiman Long <Waiman.Long@hp.com>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression
Date: Mon, 7 Sep 2015 09:32:26 +1000	[thread overview]
Message-ID: <20150906233226.GO26895@dastard> (raw)
In-Reply-To: <20150904152523.GR18673@twins.programming.kicks-ass.net>

On Fri, Sep 04, 2015 at 05:25:23PM +0200, Peter Zijlstra wrote:
> Something like so...
> 
> ---
> Subject: locking: Fix virt test-and-set lock implementation
> 
> Dave ran into horrible performance on a VM without PARAVIRT_SPINLOCKS
> set and Linus noted that the test-and-set implementation was retarded.
> 
> One should spin on the variable with a load, not a rmw.
> 
> While there, remove the queued from the name, as the lock isn't queued
> at all, but a simple test-and-set.
> 
> Reported-by: Dave Chinner <david@fromorbit.com>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

FSUse%        Count         Size    Files/sec     App Overhead
     0      1600000            0     319511.8          9398733
     0      3200000            0     301517.9          9516230
     0      4800000            0     300357.6          9676651
     0      6400000            0     282167.8         11513255

Looks OK.

Tested-by: Dave Chinner <david@fromorbit.com>

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  reply	other threads:[~2015-09-06 23:32 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-04  5:48 [4.2, Regression] Queued spinlocks cause major XFS performance regression Dave Chinner
2015-09-04  6:39 ` Linus Torvalds
2015-09-04  7:11   ` Dave Chinner
2015-09-04  7:31     ` Juergen Gross
2015-09-04  7:55     ` Peter Zijlstra
2015-09-04  8:29     ` Dave Chinner
2015-09-04 15:05       ` Linus Torvalds
2015-09-04 15:14         ` Peter Zijlstra
2015-09-04 15:21           ` Linus Torvalds
2015-09-04 15:30             ` Peter Zijlstra
2015-09-04 15:54               ` Peter Zijlstra
2015-09-10  2:06                 ` Waiman Long
2015-09-04 15:58               ` Linus Torvalds
2015-09-05 17:45                 ` Peter Zijlstra
2015-09-04 15:25           ` Peter Zijlstra
2015-09-06 23:32             ` Dave Chinner [this message]
2015-09-07  0:05             ` Davidlohr Bueso
2015-09-07  6:57               ` Peter Zijlstra
2015-09-07 20:45                 ` Linus Torvalds
2015-09-08  6:37                   ` Davidlohr Bueso
2015-09-08 10:05                   ` Peter Zijlstra
2015-09-08 17:45                     ` Linus Torvalds
2015-09-13 10:55             ` [tip:locking/core] locking/qspinlock/x86: Fix performance regression under unaccelerated VMs tip-bot for Peter Zijlstra
2015-09-04  7:39   ` [4.2, Regression] Queued spinlocks cause major XFS performance regression Peter Zijlstra
2015-09-04  8:12     ` Dave Chinner
2015-09-04 11:32       ` Peter Zijlstra
2015-09-04 22:03         ` Dave Chinner
2015-09-06 23:47         ` Dave Chinner
2015-09-10  2:09           ` Waiman Long
     [not found]         ` <CAC=cRTOraeOeu3Z8C1qx6w=GMSzD_4VevrEzn0mMhrqy=7n3wQ@mail.gmail.com>
     [not found]           ` <56094F05.4090809@hpe.com>
2015-09-29  0:47             ` huang ying
2015-09-29  2:57               ` Waiman Long
2015-09-10  2:01 ` Waiman Long

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