Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932205AbbFQOb4 (ORCPT ); Wed, 17 Jun 2015 10:31:56 -0400 Received: from mail-wg0-f49.google.com ([74.125.82.49]:34250 "EHLO mail-wg0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757316AbbFQObs (ORCPT ); Wed, 17 Jun 2015 10:31:48 -0400 Message-ID: <1434551504.23509.21.camel@gmail.com> Subject: Re: [PATCH v2] futex: lower the lock contention on the HB lock during wake up From: Mike Galbraith To: Sebastian Andrzej Siewior Cc: Davidlohr Bueso , Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Steven Rostedt , "Paul E. McKenney" , linux-kernel@vger.kernel.org Date: Wed, 17 Jun 2015 16:31:44 +0200 In-Reply-To: <558183FB.7060808@linutronix.de> References: <1432056298-18738-1-git-send-email-dave@stgolabs.net> <1432056298-18738-2-git-send-email-dave@stgolabs.net> <20150616192911.GA19500@linutronix.de> <1434484226.1903.19.camel@stgolabs.net> <20150617083350.GA2433@linutronix.de> <1434550624.23509.18.camel@gmail.com> <558183FB.7060808@linutronix.de> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1806 Lines: 37 On Wed, 2015-06-17 at 16:28 +0200, Sebastian Andrzej Siewior wrote: > On 06/17/2015 04:17 PM, Mike Galbraith wrote: > > On Wed, 2015-06-17 at 10:33 +0200, Sebastian Andrzej Siewior wrote: > >> wake_futex_pi() wakes the task before releasing the hash bucket lock > >> (HB). The first thing the woken up task usually does is to acquire the > >> lock which requires the HB lock. On SMP Systems this leads to blocking > >> on the HB lock which is released by the owner shortly after. > >> This patch rearranges the unlock path by first releasing the HB lock and > >> then waking up the task. > >> > >> [bigeasy: redo ontop of lockless wake-queues] > >> Signed-off-by: Thomas Gleixner > >> Signed-off-by: Sebastian Andrzej Siewior > > > > 4.1-rc8-rt4 contains this via 4.0-rt4, and seems fine on my 64 core > > DL980. I ran a few iterations of futextests and stockfish, then mixed > > two loops of futextest at different rt prios, with stockfish also rt, > > and ltplight as tossed in as... crack filler. Box is still doing that, > > is way too busy, but not griping about it. > > There are two patches mostly doing the same thing. The patch posted > here is a redo ontop of "lockless wake-queues". It does hb-unlock, > wakeup, de-boost. The patch merged into -RT is the original approach > not using "lockless wake-queues" and performing wakeup, hb-unlock, > de-boost. > > I plan to get into -RT the final solution once it hits upstream. OK, a glance wasn't enough. Guess I can let tired ole box rest. -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/