From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753548AbcD1Jho (ORCPT ); Thu, 28 Apr 2016 05:37:44 -0400 Received: from merlin.infradead.org ([205.233.59.134]:46734 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753071AbcD1Jhm (ORCPT ); Thu, 28 Apr 2016 05:37:42 -0400 Date: Thu, 28 Apr 2016 11:37:33 +0200 From: Peter Zijlstra To: Yuyang Du Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, bsegall@google.com, pjt@google.com, morten.rasmussen@arm.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, lizefan@huawei.com, umgwanakikbuti@gmail.com Subject: Re: [PATCH v3 6/6] sched/fair: Move (inactive) option from code to config Message-ID: <20160428093733.GX3430@twins.programming.kicks-ass.net> References: <1459829551-21625-1-git-send-email-yuyang.du@intel.com> <1459829551-21625-7-git-send-email-yuyang.du@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1459829551-21625-7-git-send-email-yuyang.du@intel.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 05, 2016 at 12:12:31PM +0800, Yuyang Du wrote: > The option of increased load resolution (fixed point arithmetic range) is > unconditionally deactivated with #if 0. But since it may still be used > somewhere (e.g., in Google), we want to keep this option. > > Regardless, there should be a way to express this option. Considering the > current circumstances, the reconciliation is we define a config > CONFIG_CFS_INCREASE_LOAD_RANGE and it depends on FAIR_GROUP_SCHED and > 64BIT and BROKEN. > > Suggested-by: Ingo Molnar So I'm very tempted to simply, unconditionally, reinstate this larger range for everything CONFIG_64BIT && CONFIG_FAIR_GROUP_SCHED. There was but the single claim on increased power usage, nobody could reproduce / analyze and Google has been running with this for years now. Furthermore, it seems to be leading to the obvious problems on bigger machines where we basically run out of precision by the sheer number of cpus (nr_cpus ~ SCHED_LOAD_SCALE and stuff comes apart quickly).