From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755578AbaCYWfY (ORCPT ); Tue, 25 Mar 2014 18:35:24 -0400 Received: from mga02.intel.com ([134.134.136.20]:5746 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752126AbaCYWfW (ORCPT ); Tue, 25 Mar 2014 18:35:22 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,730,1389772800"; d="scan'208";a="507508589" From: Andi Kleen To: Stephane Eranian Cc: Arnaldo Carvalho de Melo , Ingo Molnar , LKML , Peter Zijlstra , Namhyung Kim , Jiri Olsa Subject: Re: [PATCH] tools, perf: Allow the user to disable time stamps References: <1395780272-27106-1-git-send-email-andi@firstfloor.org> <20140325210109.GH15074@tassilo.jf.intel.com> Date: Tue, 25 Mar 2014 15:34:52 -0700 In-Reply-To: (Stephane Eranian's message of "Tue, 25 Mar 2014 23:15:05 +0100") Message-ID: <87wqfhoqk3.fsf@tassilo.jf.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Stephane Eranian writes: >> > But getting the mmaps at the right moment is crucial for some apps > especially if address space is recycled otherwise symbolization > may be incorrect. Yes that is why it is only an option and not default. You need to know what you're doing. BTW I think the recycle case is not very likely on non JIT. >> You're right for some special analysis it matters, that is why >> it is only an option. >> >> But for the standard "only care about perf report and >> don't care about about program startup" case it's a nice saving. >> > How do you know in advance you won't need mmap ordering? When I measure a long running process and I know it doesn't fork/dlopen/jit. Using --initial-delay also helps to skip the startup phase or attaching later. I believe it's actually a good choice for most non forky workloads. But yes it cannot be made default. -Andi -- ak@linux.intel.com -- Speaking for myself only