Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757349AbcDMDkY (ORCPT ); Tue, 12 Apr 2016 23:40:24 -0400 Received: from mx2.suse.de ([195.135.220.15]:47829 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757078AbcDMDkW (ORCPT ); Tue, 12 Apr 2016 23:40:22 -0400 Message-ID: <1460518820.3780.37.camel@suse.de> Subject: Re: [PATCH RFC] select_idle_sibling experiments From: Mike Galbraith To: Matt Fleming , Chris Mason , Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org Date: Wed, 13 Apr 2016 05:40:20 +0200 In-Reply-To: <20160412214502.GI2829@codeblueprint.co.uk> References: <20160405180822.tjtyyc3qh4leflfj@floor.thefacebook.com> <1459927644.5612.41.camel@suse.de> <20160409173034.GA85074@clm-mbp.thefacebook.com> <20160412214502.GI2829@codeblueprint.co.uk> 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 Content-Length: 917 Lines: 23 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. -Mike