From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754631AbcFQGVJ (ORCPT ); Fri, 17 Jun 2016 02:21:09 -0400 Received: from mail-wm0-f43.google.com ([74.125.82.43]:37939 "EHLO mail-wm0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751114AbcFQGVH (ORCPT ); Fri, 17 Jun 2016 02:21:07 -0400 Message-ID: <1466144462.3223.102.camel@gmail.com> Subject: Re: [patch] sched/fair: Use instantaneous load in wakeup paths From: Mike Galbraith To: Yuyang Du Cc: Peter Zijlstra , LKML Date: Fri, 17 Jun 2016 08:21:02 +0200 In-Reply-To: <1466080888.2278.30.camel@gmail.com> References: <1465891111.1694.13.camel@gmail.com> <20160614224218.GK8105@intel.com> <1465974093.4219.14.camel@gmail.com> <1466077593.2278.23.camel@gmail.com> <1466078681.2278.26.camel@gmail.com> <1466080888.2278.30.camel@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Here are some schbench runs on an 8x8 box to show that longish run/sleep period corner I mentioned. vogelweide:~/:[1]# for i in `seq 5`; do schbench -m 8 -t 1 -a -r 10 2>&1 | grep 'threads 8'; done cputime 30000 threads 8 p99 68 cputime 30000 threads 8 p99 46 cputime 30000 threads 8 p99 46 cputime 30000 threads 8 p99 45 cputime 30000 threads 8 p99 49 vogelweide:~/:[0]# echo NO_WAKE_INSTANTANEOUS_LOAD > /sys/kernel/debug/sched_features vogelweide:~/:[0]# for i in `seq 5`; do schbench -m 8 -t 1 -a -r 10 2>&1 | grep 'threads 8'; done cputime 30000 threads 8 p99 9968 cputime 30000 threads 8 p99 10224 vogelweide:~/:[0]# Using instantaneous load, we fill the box every time, without, we stack every time. This was with Peter's select_idle_sibling() rewrite applied as well, but you can see that it does matter. That doesn't mean I think my patch should immediately fly upstream 'course, who knows, there may be a less messy way to deal with it, or, as already stated, maybe it just doesn't matter enough to the real world to even bother with. -Mike