From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8D4EC433EF for ; Fri, 22 Oct 2021 11:05:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD258610C8 for ; Fri, 22 Oct 2021 11:05:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232711AbhJVLH4 (ORCPT ); Fri, 22 Oct 2021 07:07:56 -0400 Received: from outbound-smtp11.blacknight.com ([46.22.139.106]:37867 "EHLO outbound-smtp11.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232560AbhJVLHz (ORCPT ); Fri, 22 Oct 2021 07:07:55 -0400 Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp11.blacknight.com (Postfix) with ESMTPS id 605831C480F for ; Fri, 22 Oct 2021 12:05:36 +0100 (IST) Received: (qmail 15570 invoked from network); 22 Oct 2021 11:05:36 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.17.29]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 22 Oct 2021 11:05:36 -0000 Date: Fri, 22 Oct 2021 12:05:34 +0100 From: Mel Gorman To: Mike Galbraith Cc: Peter Zijlstra , Ingo Molnar , Vincent Guittot , Valentin Schneider , Aubrey Li , Barry Song , Srikar Dronamraju , LKML Subject: Re: [PATCH 1/2] sched/fair: Couple wakee flips with heavy wakers Message-ID: <20211022110534.GJ3959@techsingularity.net> References: <20211021145603.5313-1-mgorman@techsingularity.net> <20211021145603.5313-2-mgorman@techsingularity.net> <37d8c167df66a1ead16b699115548ca376494c0c.camel@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <37d8c167df66a1ead16b699115548ca376494c0c.camel@gmx.de> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 22, 2021 at 12:26:08PM +0200, Mike Galbraith wrote: > On Thu, 2021-10-21 at 15:56 +0100, Mel Gorman wrote: > > > > From additional tests on various servers, the impact is machine dependant > > but generally this patch improves the situation. > > > > hackbench-process-pipes > >                           5.15.0-rc3             5.15.0-rc3 > >                              vanilla  sched-wakeeflips-v1r1 > > Amean     1        0.3667 (   0.00%)      0.3890 (  -6.09%) > > Amean     4        0.5343 (   0.00%)      0.5217 (   2.37%) > > Amean     7        0.5300 (   0.00%)      0.5387 (  -1.64%) > > Amean     12       0.5737 (   0.00%)      0.5443 (   5.11%) > > Amean     21       0.6727 (   0.00%)      0.6487 (   3.57%) > > Amean     30       0.8583 (   0.00%)      0.8033 (   6.41%) > > Amean     48       1.3977 (   0.00%)      1.2400 *  11.28%* > > Amean     79       1.9790 (   0.00%)      1.8200 *   8.03%* > > Amean     110      2.8020 (   0.00%)      2.5820 *   7.85%* > > Amean     141      3.6683 (   0.00%)      3.2203 *  12.21%* > > Amean     172      4.6687 (   0.00%)      3.8200 *  18.18%* > > Amean     203      5.2183 (   0.00%)      4.3357 *  16.91%* > > Amean     234      6.1077 (   0.00%)      4.8047 *  21.33%* > > Amean     265      7.1313 (   0.00%)      5.1243 *  28.14%* > > Amean     296      7.7557 (   0.00%)      5.5940 *  27.87%* > > > > While different machines showed different results, in general > > there were much less CPU migrations of tasks > > Patchlet helped hackbench? That's.. unexpected (at least by me). > I didn't analyse in depth and other machines do not show as dramatic a difference but it's likely due to timings of tasks getting wakeup preempted. On a 2-socket cascadelake machine the difference was -7.4% to 7.66% depending on group count. The second biggest loss was -0.71% and more gains than losses. In each case, CPU migrations and system CPU usage are reduced. The big difference here is likely because the machine is Zen 3 and has multiple LLCs per cache so it suffers more if there are imbalances between LLCs that wouldn't be visible on most Intel machines with 1 LLC per socket. > > tbench4 > >                            5.15.0-rc3             5.15.0-rc3 > >                               vanilla  sched-wakeeflips-v1r1 > > Hmean     1         824.05 (   0.00%)      802.56 *  -2.61%* > > Hmean     2        1578.49 (   0.00%)     1645.11 *   4.22%* > > Hmean     4        2959.08 (   0.00%)     2984.75 *   0.87%* > > Hmean     8        5080.09 (   0.00%)     5173.35 *   1.84%* > > Hmean     16       8276.02 (   0.00%)     9327.17 *  12.70%* > > Hmean     32      15501.61 (   0.00%)    15925.55 *   2.73%* > > Hmean     64      27313.67 (   0.00%)    24107.81 * -11.74%* > > Hmean     128     32928.19 (   0.00%)    36261.75 *  10.12%* > > Hmean     256     35434.73 (   0.00%)    38670.61 *   9.13%* > > Hmean     512     50098.34 (   0.00%)    53243.75 *   6.28%* > > Hmean     1024    69503.69 (   0.00%)    67425.26 *  -2.99%* > > > > Bit of a mixed bag but wins more than it loses. > > Hm. If patchlet repeatably impacts buddy pairs one way or the other, > it should probably be tossed out the nearest window. > I don't see how buddy pairing would be impacted although there is likely differences in the degree tasks get preempted due to pulling tasks. -- Mel Gorman SUSE Labs