Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754661AbdDLPOa (ORCPT ); Wed, 12 Apr 2017 11:14:30 -0400 Received: from mail-wr0-f194.google.com ([209.85.128.194]:34963 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753254AbdDLPO0 (ORCPT ); Wed, 12 Apr 2017 11:14:26 -0400 Date: Wed, 12 Apr 2017 17:14:23 +0200 From: Frederic Weisbecker To: Thomas Gleixner Cc: Wanpeng Li , Mike Galbraith , Rik van Riel , Luiz Capitulino , "linux-kernel@vger.kernel.org" , Peter Zijlstra Subject: Re: [BUG nohz]: wrong user and system time accounting Message-ID: <20170412151421.GF21309@lerouge> References: <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> <20170412131818.GB21309@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: 775 Lines: 24 On Wed, Apr 12, 2017 at 04:57:58PM +0200, Thomas Gleixner wrote: > On Wed, 12 Apr 2017, Frederic Weisbecker wrote: > > On Tue, Apr 11, 2017 at 04:22:48PM +0200, Thomas Gleixner wrote: > > > It's not different from the current jiffies based stuff at all. Same > > > failure mode. > > > > Yes you're right, I got confused again. So to fix this we could do our snapshots > > at a frequency lower than HZ but still high enough to avoid overhead. > > > > Something like TICK_NSEC / 2 ? > > If you are using TSC anyway then you can do proper accumulation for both > system and user and only account the data when the accumulation is more > than a jiffie. Sounds nice, and accumulation shouldn't introduce too much overhead. Let's try that. Thanks. > > Thanks, > > tglx >