Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756787AbbHZRL3 (ORCPT ); Wed, 26 Aug 2015 13:11:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47503 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751979AbbHZRLZ (ORCPT ); Wed, 26 Aug 2015 13:11:25 -0400 Date: Wed, 26 Aug 2015 19:08:52 +0200 From: Oleg Nesterov To: Jason Low Cc: Andrew Morton , Peter Zijlstra , Ingo Molnar , Thomas Gleixner , "Paul E. McKenney" , linux-kernel@vger.kernel.org, Frederic Weisbecker , Linus Torvalds , Davidlohr Bueso , Steven Rostedt , Terry Rudd , Rik van Riel , Scott J Norton Subject: Re: [PATCH 0/3] timer: Improve itimers scalability Message-ID: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1440606804.23728.85.camel@j-VirtualBox> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1473 Lines: 39 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 ;) However, I thinks the patches are fine. Reviewed-by: Oleg Nesterov -- 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/