Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933810AbbLOV4G (ORCPT ); Tue, 15 Dec 2015 16:56:06 -0500 Received: from mail-pf0-f175.google.com ([209.85.192.175]:34269 "EHLO mail-pf0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933678AbbLOV4E (ORCPT ); Tue, 15 Dec 2015 16:56:04 -0500 Subject: Re: [PATCH] sched/fair: fix mul overflow on 32-bit systems To: Yuyang Du , Peter Zijlstra References: <1449838518-26543-1-git-send-email-aryabinin@virtuozzo.com> <20151211132551.GO6356@twins.programming.kicks-ass.net> <20151211133612.GG6373@twins.programming.kicks-ass.net> <566AD6E1.2070005@virtuozzo.com> <20151211175751.GA27552@e105550-lin.cambridge.arm.com> <20151213224224.GC28098@intel.com> <20151214115453.GN6357@twins.programming.kicks-ass.net> <20151215022229.GF28098@intel.com> Cc: Morten Rasmussen , Andrey Ryabinin , mingo@redhat.com, linux-kernel@vger.kernel.org, Paul Turner , Ben Segall From: Steve Muckle X-Enigmail-Draft-Status: N1110 Message-ID: <56708C71.90701@linaro.org> Date: Tue, 15 Dec 2015 13:56:01 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20151215022229.GF28098@intel.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 932 Lines: 22 On 12/14/2015 06:22 PM, Yuyang Du wrote: > what if we just init the util_avg to 0? With scheduler-guided frequency [1] we will rely on the initial util_avg value to determine the CPU frequency response when new tasks are created. There is sure to be a lot of debate on what sort of default policy is used (and how much that can be changed with tunables). IMO at least for now, new tasks should cause the target CPU to go to fmax, especially given how slow PELT is to respond to changes in task behavior. This would imply leaving the initial task util_avg at 100% (or the equivalent necessary to take care of the overflow issues). [1] https://lkml.org/lkml/2015/12/9/35 thanks, Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/