Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751737AbdLVIE5 (ORCPT ); Fri, 22 Dec 2017 03:04:57 -0500 Received: from mail-io0-f181.google.com ([209.85.223.181]:42169 "EHLO mail-io0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750961AbdLVIE4 (ORCPT ); Fri, 22 Dec 2017 03:04:56 -0500 X-Google-Smtp-Source: ACJfBotoVPHMdcCzb9rrZW8AnStuf3bjLrizjp4p4KCTbV0y5Xenvfv4LH3zx/siRDukuC+n/EG3EaNTEQjQk5+ypkM= MIME-Version: 1.0 In-Reply-To: <20171222075643.zrdsayvcpovysnre@hirez.programming.kicks-ass.net> References: <20171221102139.177253391@infradead.org> <20171221102235.088181011@infradead.org> <20171222075643.zrdsayvcpovysnre@hirez.programming.kicks-ass.net> From: Vincent Guittot Date: Fri, 22 Dec 2017 09:04:35 +0100 Message-ID: Subject: Re: [RFC PATCH 2/5] sched: Add NOHZ_STATS_KICK To: Peter Zijlstra Cc: Ingo Molnar , linux-kernel , Brendan Jackman , Dietmar Eggemann , Morten Rasmussen Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 846 Lines: 24 On 22 December 2017 at 08:56, Peter Zijlstra wrote: > On Thu, Dec 21, 2017 at 05:23:27PM +0100, Vincent Guittot wrote: >> Hi Peter, >> >> I think that part of the proposal is missing. >> >> One goal of the patchset was to kick an update of the stats of idle >> cpu when a task wake up on a cpu but the statistic has not been >> updated for a while. >> >> That's why there where a call to nohz_kick_needed in the proposal to >> kick ilb but only for updating blocked load and not a full idle load >> balance >> >> I can't find this call any more in your patchset > > Yeah, I took it out because it didn't make sense to me. If you're waking > to a stale CPU, you're too late. I agree that's it's too late for the current wake up but that's the trade off with delaying the wake up until all blocked load has been updated. >