From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751399AbcEAHMh (ORCPT ); Sun, 1 May 2016 03:12:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:41132 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750789AbcEAHMg (ORCPT ); Sun, 1 May 2016 03:12:36 -0400 Message-ID: <1462086753.9717.29.camel@suse.de> Subject: Re: sched: tweak select_idle_sibling to look for idle threads From: Mike Galbraith To: Peter Zijlstra , Chris Mason , Ingo Molnar , Matt Fleming , linux-kernel@vger.kernel.org Date: Sun, 01 May 2016 09:12:33 +0200 In-Reply-To: <20160430124731.GE2975@worktop.cust.blueprintrf.com> References: <20160405180822.tjtyyc3qh4leflfj@floor.thefacebook.com> <20160409190554.honue3gtian2p6vr@floor.thefacebook.com> <20160430124731.GE2975@worktop.cust.blueprintrf.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 On Sat, 2016-04-30 at 14:47 +0200, Peter Zijlstra wrote: > On Sat, Apr 09, 2016 at 03:05:54PM -0400, Chris Mason wrote: > > select_task_rq_fair() can leave cpu utilization a little lumpy, > > especially as the workload ramps up to the maximum capacity of the > > machine. The end result can be high p99 response times as apps > > wait to get scheduled, even when boxes are mostly idle. > > > > I wrote schbench to try and measure this: > > > > git://git.kernel.org/pub/scm/linux/kernel/git/mason/schbench.git > > Can you guys have a play with this; I think one and two node tbench are > good, but I seem to be getting significant run to run variance on that, > so maybe I'm not doing it right. Nah, tbench is just variance prone. It got dinged up at clients=cores on my desktop box, on 4 sockets the high end got seriously dinged up. tbench 1 x i4790 master avg 1 714 684 688 695 1.000 2 1260 1234 1284 1259 1.000 4 2238 2301 2286 2275 1.000 8 3388 3418 3396 3400 1.000 masterx 1 690 701 701 697 1.002 2 1287 1332 1235 1284 1.019 4 2014 2006 1999 2006 0.881 8 3388 3385 3404 3392 0.997 4 x E7-8890 master avg 1 524 524 523 523 1.000 2 1049 1053 1045 1049 1.000 4 2064 2081 2091 2078 1.000 8 3737 3813 3746 3765 1.000 16 7129 7028 7082 7079 1.000 32 13718 13730 13578 13675 1.000 64 21397 21435 21519 21450 1.000 128 39846 38397 39026 39089 1.000 256 59509 59797 59344 59550 1.000 masterx avg 1 505 507 501 504 0.963 1.000 2 1036 1027 1039 1034 0.985 1.000 4 1977 2001 1992 1990 0.957 1.000 8 3734 3802 3778 3771 1.001 1.000 16 7124 7079 7071 7091 1.001 1.000 32 13549 13758 13364 13557 0.991 1.000 64 21975 22161 22100 22078 1.029 1.000 128 23066 23044 23028 23046 0.589 1.000 256 29905 29630 30753 30096 0.505 1.000 masterx NO_IDLE_CORE avg 1 500 521 502 507 0.969 1.005 2 1012 996 1043 1017 0.969 0.983 4 1988 1992 1995 1991 0.958 1.000 8 3834 3758 3671 3754 0.997 0.995 16 7160 7206 7168 7178 1.013 1.012 32 13788 13773 13672 13744 1.005 1.013 64 21771 21845 21826 21814 1.016 0.988 128 23248 23136 23133 23172 0.592 1.005 256 28683 30013 31850 30182 0.506 1.002