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
next prev parent 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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