Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753031AbdHOSkp (ORCPT ); Tue, 15 Aug 2017 14:40:45 -0400 Received: from foss.arm.com ([217.140.101.70]:56080 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752785AbdHOSkk (ORCPT ); Tue, 15 Aug 2017 14:40:40 -0400 Date: Tue, 15 Aug 2017 19:40:40 +0100 From: Will Deacon To: Vikram Mulukutla Cc: qiaozhou , Thomas Gleixner , John Stultz , sboyd@codeaurora.org, LKML , Wang Wilbur , Marc Zyngier , Peter Zijlstra , linux-kernel-owner@vger.kernel.org, sudeep.holla@arm.com Subject: Re: [Question]: try to fix contention between expire_timers and try_to_del_timer_sync Message-ID: <20170815184039.GE10801@arm.com> References: <3d2459c7-defd-a47e-6cea-007c10cecaac@asrmicro.com> <20170728092831.GA24839@arm.com> <2aa9684cf9c889ee9fdc8550b4388af6@codeaurora.org> <20170731131321.GB1737@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 973 Lines: 28 Hi Vikram, On Thu, Aug 03, 2017 at 04:25:12PM -0700, Vikram Mulukutla wrote: > On 2017-07-31 06:13, Will Deacon wrote: > >On Fri, Jul 28, 2017 at 12:09:38PM -0700, Vikram Mulukutla wrote: > >>On 2017-07-28 02:28, Will Deacon wrote: > >>>On Thu, Jul 27, 2017 at 06:10:34PM -0700, Vikram Mulukutla wrote: > > >>> > >>This does seem to help. Here's some data after 5 runs with and without > >>the > >>patch. > > > >Blimey, that does seem to make a difference. Shame it's so ugly! Would you > >be able to experiment with other values for CPU_RELAX_WFE_THRESHOLD? I had > >it set to 10000 in the diff I posted, but that might be higher than > >optimal. > >It would be interested to see if it correlates with num_possible_cpus() > >for the highly contended case. > > > >Will > > Sorry for the late response - I should hopefully have some more data with > different thresholds before the week is finished or on Monday. Did you get anywhere with the threshold heuristic? Will