From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753364AbcDMP4h (ORCPT ); Wed, 13 Apr 2016 11:56:37 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:2217 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751123AbcDMP4f (ORCPT ); Wed, 13 Apr 2016 11:56:35 -0400 Date: Wed, 13 Apr 2016 11:54:40 -0400 From: Chris Mason To: Mike Galbraith CC: Matt Fleming , Peter Zijlstra , Ingo Molnar , Subject: Re: [PATCH RFC] select_idle_sibling experiments Message-ID: <20160413155440.xmlzxbrd6flwtli7@floor.thefacebook.com> Mail-Followup-To: Chris Mason , Mike Galbraith , Matt Fleming , Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org References: <20160405180822.tjtyyc3qh4leflfj@floor.thefacebook.com> <1459927644.5612.41.camel@suse.de> <20160409173034.GA85074@clm-mbp.thefacebook.com> <20160412214502.GI2829@codeblueprint.co.uk> <1460518820.3780.37.camel@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1460518820.3780.37.camel@suse.de> User-Agent: Mutt/1.5.23.1 (2014-03-12) X-Originating-IP: [192.168.52.123] X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-04-13_08:,, signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 13, 2016 at 05:40:20AM +0200, Mike Galbraith wrote: > On Tue, 2016-04-12 at 22:45 +0100, Matt Fleming wrote: > > On Sat, 09 Apr, at 01:30:34PM, Chris Mason wrote: > > > > > > [ nohz throttling patch ] > > > > > > I tested the nohz throttle two different ways, first with schbench's > > > pipe simulation, it's easily 8% faster with messages bouncing between > > > cpus. > > > > > > In production it's hard to pick a single number because the benchmarks > > > produce latency curves as the workload scales up in RPS. The benefits > > > range from 2-9% depending on the metric. It's a nice win, and I'd love to > > > see it go in. > > > > Do we have any idea what the tradeoff is against power consumption for > > throttling nohz? > > That's measurable with the built in super duper watt meter gizmo > (turbostat). It should be dinky but existent, could be given an off > button for particularly attentive laptop drivers to poke. Servers > drivers are unlikely to care given the performance win. Our power sensors show its basically a wash during the production benchmark runs. Which makes sense because its really only blinking on/off at very high frequency. -chris