Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756845AbbHZWHd (ORCPT ); Wed, 26 Aug 2015 18:07:33 -0400 Received: from g2t2354.austin.hp.com ([15.217.128.53]:55011 "EHLO g2t2354.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752754AbbHZWHb (ORCPT ); Wed, 26 Aug 2015 18:07:31 -0400 Message-ID: <1440626847.23728.122.camel@j-VirtualBox> Subject: Re: [PATCH 0/3] timer: Improve itimers scalability From: Jason Low To: Oleg Nesterov Cc: Andrew Morton , Peter Zijlstra , Ingo Molnar , Thomas Gleixner , "Paul E. McKenney" , linux-kernel@vger.kernel.org, Frederic Weisbecker , Linus Torvalds , Steven Rostedt , Rik van Riel , Scott J Norton , jason.low2@hp.com, hideaki.kimura@hpe.com Date: Wed, 26 Aug 2015 15:07:27 -0700 In-Reply-To: <20150826170851.GA5264@redhat.com> References: <1440559068-29680-1-git-send-email-jason.low2@hp.com> <20150825202710.d960a928.akpm@linux-foundation.org> <1440606804.23728.85.camel@j-VirtualBox> <20150826170851.GA5264@redhat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1697 Lines: 45 On Wed, 2015-08-26 at 19:08 +0200, Oleg Nesterov wrote: > On 08/26, Jason Low wrote: > > > > Hi Andrew, > > > > On Tue, 2015-08-25 at 20:27 -0700, Andrew Morton wrote: > > > On Tue, 25 Aug 2015 20:17:45 -0700 Jason Low wrote: > > > > > > > When running a database workload on a 16 socket machine, there were > > > > scalability issues related to itimers. > > > > > > > > Commit 1018016c706f addressed the issue with the thread_group_cputimer > > > > spinlock taking up a significant portion of total run time. > > > > > > > > This patch series address the other issue where a lot of time is spent > > > > trying to acquire the sighand lock. It was found in some cases that > > > > 200+ threads were simultaneously contending for the same sighand lock, > > > > reducing throughput by more than 30%. > > > > > > Does this imply that the patchset increased the throughput of this > > > workload by 30%? > > > > > > And is this test case realistic? If not, what are the benefits on a > > > real-world workload? > > > > Yes, the test case with the database workload is realistic. > > Can't resists, sorry... to me the very idea to use the process wide posix- > cpu-timers on performance critical application doesn't look realistic ;) I will let Hideaki elaborate more regarding the issue at the application level. > However, I thinks the patches are fine. > > > Reviewed-by: Oleg Nesterov Thanks for reviewing! -- 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/