From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755559AbcANW13 (ORCPT ); Thu, 14 Jan 2016 17:27:29 -0500 Received: from eu-smtp-delivery-143.mimecast.com ([146.101.78.143]:40176 "EHLO eu-smtp-delivery-143.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754174AbcANWXx convert rfc822-to-8bit (ORCPT ); Thu, 14 Jan 2016 17:23:53 -0500 Subject: Re: [RFC PATCH 0/4] sched: Improve cpu load accounting with nohz To: Peter Zijlstra References: <1452700891-21807-1-git-send-email-fweisbec@gmail.com> <569810C4.7090900@arm.com> <20160114212704.GJ6357@twins.programming.kicks-ass.net> CC: Frederic Weisbecker , LKML , Byungchul Park , Chris Metcalf , Thomas Gleixner , Luiz Capitulino , Christoph Lameter , "Paul E . 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charset=WINDOWS-1252; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/14/2016 09:27 PM, Peter Zijlstra wrote: > On Thu, Jan 14, 2016 at 09:19:00PM +0000, Dietmar Eggemann wrote: >> @@ -4346,7 +4346,10 @@ static void __update_cpu_load(struct rq *this_rq, unsigned long this_load, >> >> /* scale is effectively 1 << i now, and >> i divides by scale */ >> >> - old_load = this_rq->cpu_load[i] - tickless_load; >> + if (this_rq->cpu_load[i] > tickless_load) >> + old_load = this_rq->cpu_load[i] - tickless_load; >> + else >> + old_load = 0; > > Yeah, yuck. That'd go bad quick. > ... because I set it to 0? But after the decay function we add tickless_load to old_load. Maybe in case tickless_load > this_rq->cpu_load[i] we decay this_rq->cpu_load[i] and do not add tickless_load afterwards. IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.