linux-kernel - Re: bisected: futex regression >= 3.14 - was - Slowdown due to threads bouncing between HT cores

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Message-ID: <20141008170513.GA13720@sesse.net>
Date:	Wed, 8 Oct 2014 19:05:13 +0200
From:	"Steinar H. Gunderson" <sgunderson@...foot.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Mike Galbraith <umgwanakikbuti@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: bisected: futex regression >= 3.14 - was - Slowdown due to
 threads bouncing between HT cores

On Wed, Oct 08, 2014 at 01:04:01PM -0400, Linus Torvalds wrote:
> So like Thomas, I would suspect a race condition in the futex use, and
> then the exact futex implementation details are just exposing it
> incidentally.

FWIW, Stockfish does not use futex directly; it uses pthreads (or Win32
threads if you are on that OS :-) ). That doesn't preclude a race condition
somewhere, of course.

/* Steinar */
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Homepage: http://www.sesse.net/
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