From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org by pdx-caf-mail.web.codeaurora.org (Dovecot) with LMTP id RCkmFcbJGVvlDgAAmS7hNA ; Fri, 08 Jun 2018 00:12:12 +0000 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 4AEDB6074D; Fri, 8 Jun 2018 00:12:12 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on pdx-caf-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by smtp.codeaurora.org (Postfix) with ESMTP id B884560290; Fri, 8 Jun 2018 00:12:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org B884560290 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752456AbeFHAMJ (ORCPT + 25 others); Thu, 7 Jun 2018 20:12:09 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:54602 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752178AbeFHAMI (ORCPT ); Thu, 7 Jun 2018 20:12:08 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AE66CBB42F; Fri, 8 Jun 2018 00:12:07 +0000 (UTC) Received: from krava (ovpn-204-19.brq.redhat.com [10.40.204.19]) by smtp.corp.redhat.com (Postfix) with SMTP id BE59B1117648; Fri, 8 Jun 2018 00:12:04 +0000 (UTC) Date: Fri, 8 Jun 2018 02:12:03 +0200 From: Jiri Olsa To: Stephane Eranian Cc: Andi Kleen , Jiri Olsa , Arnaldo Carvalho de Melo , Peter Zijlstra , LKML , Ingo Molnar , Namhyung Kim , David Ahern , Alexander Shishkin , Milian Wolff , frederic@kernel.org Subject: Re: [PATCH 09/10] perf/cputime: Don't stop idle tick if there's live cputime event Message-ID: <20180608001203.GB12322@krava> References: <20180606221513.11302-1-jolsa@kernel.org> <20180606221513.11302-10-jolsa@kernel.org> <20180607154522.hyjmxn3q6zgcvsnx@two.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Fri, 08 Jun 2018 00:12:07 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Fri, 08 Jun 2018 00:12:07 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'jolsa@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 07, 2018 at 09:01:30AM -0700, Stephane Eranian wrote: > Hi Jiri, > > On Thu, Jun 7, 2018 at 8:45 AM Andi Kleen wrote: > > > > On Thu, Jun 07, 2018 at 12:15:12AM +0200, Jiri Olsa wrote: > > > Disable stopping of the idle tick when having live cputime > > > event. When the tick is disabled, the idle counts are out > > > of date until next tick/update and perf cputime PMU provides > > > misleading counts. > > > > I really don't like this. This can totally change performance > > (e.g. less Turbo due to less idle) and performance tools shouldn't > > change the performance profile drastically. > > > You do not want to change the behavior of the kernel just because you > are monitoring. > This may introduce side effects on other events which may not otherwise exist. right.. I guess we can survive few seconds of misleading idle counts and perhaps we could detect nohz is enabled and warn about this thanks, jirka