From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754321AbbJPRe0 (ORCPT ); Fri, 16 Oct 2015 13:34:26 -0400 Received: from g2t4619.austin.hp.com ([15.73.212.82]:35888 "EHLO g2t4619.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751684AbbJPReZ (ORCPT ); Fri, 16 Oct 2015 13:34:25 -0400 X-Greylist: delayed 81237 seconds by postgrey-1.27 at vger.kernel.org; Fri, 16 Oct 2015 13:34:25 EDT Message-ID: <1445016853.2517.16.camel@j-VirtualBox> Subject: Re: [PATCH v2 0/4] timer: Improve itimers scalability From: Jason Low To: Ingo Molnar Cc: Jason Low , Peter Zijlstra , Thomas Gleixner , linux-kernel@vger.kernel.org, Oleg Nesterov , "Paul E. McKenney" , Frederic Weisbecker , Davidlohr Bueso , Steven Rostedt , Andrew Morton , George Spelvin , hideaki.kimura@hpe.com, terry.rudd@hpe.com, scott.norton@hpe.com Date: Fri, 16 Oct 2015 10:34:13 -0700 In-Reply-To: <20151016071202.GA20129@gmail.com> References: <1444849677-29330-1-git-send-email-jason.low2@hp.com> <20151015084702.GA16953@gmail.com> <1444935676.29506.15.camel@j-VirtualBox> <20151016071202.GA20129@gmail.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 On Fri, 2015-10-16 at 09:12 +0200, Ingo Molnar wrote: > * Jason Low wrote: > > > > > With this patch set (along with commit 1018016c706f mentioned above), > > > > the performance hit of itimers almost completely goes away on the > > > > 16 socket system. > > > > > > > > Jason Low (4): > > > > timer: Optimize fastpath_timer_check() > > > > timer: Check thread timers only when there are active thread timers > > > > timer: Convert cputimer->running to bool > > > > timer: Reduce unnecessary sighand lock contention > > > > > > > > include/linux/init_task.h | 3 +- > > > > include/linux/sched.h | 9 ++++-- > > > > kernel/fork.c | 2 +- > > > > kernel/time/posix-cpu-timers.c | 63 ++++++++++++++++++++++++++++----------- > > > > 4 files changed, 54 insertions(+), 23 deletions(-) > > > > > > Is there some itimers benchmark that can be used to measure the effects of these > > > changes? > > > > Yes, we also wrote a micro benchmark which generates cache misses and measures > > the average cost of each cache miss (with itimers enabled). We used this while > > writing and testing patches, since it takes a bit longer to set up and run the > > database. > > Mind posting it, so that people can stick it into a new 'perf bench timer' > subcommand, and/or reproduce your results with it? Yes, sure. At the moment, this micro benchmark is written in C++ and integrated with the database code. We can look into rewriting it into a more general program so that it can be included in perf. Thanks, Jason