From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752717AbbEHMAA (ORCPT ); Fri, 8 May 2015 08:00:00 -0400 Received: from one.firstfloor.org ([193.170.194.197]:40739 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751118AbbEHL74 (ORCPT ); Fri, 8 May 2015 07:59:56 -0400 Date: Fri, 8 May 2015 13:59:54 +0200 From: Andi Kleen To: Peter Zijlstra Cc: Andi Kleen , kan.liang@intel.com, eranian@google.com, acme@infradead.org, linux-kernel@vger.kernel.org, Andi Kleen Subject: Re: [PATCH 2/9] x86, perf: Add support for PEBSv3 profiling Message-ID: <20150508115954.GT2366@two.firstfloor.org> References: <1431039392-12589-1-git-send-email-andi@firstfloor.org> <1431039392-12589-3-git-send-email-andi@firstfloor.org> <20150508105958.GD27504@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150508105958.GD27504@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > That's wrong. It does not respect perf_event_attr::clock_id. Ok. Are we really defaulting to real time now? (CLOCK_REALTIME == 0) What happens when ntpd is active and lets the time drift? That sounds very bad for event accuracy. The clockid patch looks broken to me. At least it should default to MONOTONIC time, not just the time that happens to be 0 by accident. Also I question we really need that many different kinds of time stamps. -Andi -- ak@linux.intel.com -- Speaking for myself only.