Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934016AbdC3OSX (ORCPT ); Thu, 30 Mar 2017 10:18:23 -0400 Received: from mail-wr0-f175.google.com ([209.85.128.175]:34937 "EHLO mail-wr0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933426AbdC3OSV (ORCPT ); Thu, 30 Mar 2017 10:18:21 -0400 Date: Thu, 30 Mar 2017 16:18:17 +0200 From: Frederic Weisbecker To: Wanpeng Li Cc: Mike Galbraith , Rik van Riel , Luiz Capitulino , "linux-kernel@vger.kernel.org" , Peter Zijlstra , Thomas Gleixner Subject: Re: [BUG nohz]: wrong user and system time accounting Message-ID: <20170330141816.GE3626@lerouge> References: <20170323165512.60945ac6@redhat.com> <1490636129.8850.76.camel@redhat.com> <20170328132406.7d23579c@redhat.com> <20170329131656.1d6cb743@redhat.com> <1490818125.28917.11.camel@redhat.com> <1490848051.4167.57.camel@gmx.de> <20170330133802.GC3626@lerouge> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 758 Lines: 14 On Thu, Mar 30, 2017 at 09:59:54PM +0800, Wanpeng Li wrote: > 2017-03-30 21:38 GMT+08:00 Frederic Weisbecker : > > If it works, we may want to take that solution, likely less performance sensitive > > than using sched_clock(). In fact sched_clock() is fast, especially as we require it to > > be stable for nohz_full, but using it involves costly conversion back and forth to jiffies. > > So both Rik and you agree with the skew tick solution, I will try it > tomorrow. Btw, if we should just add random offset to the cpu in the > nohz_full mode or add random offset to all cpus like the codes above? Lets just keep it to all CPUs for simplicty. Also please add a comment that explains why we need that skew_tick on nohz_full. Thanks!