From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758968Ab3JPB6j (ORCPT ); Tue, 15 Oct 2013 21:58:39 -0400 Received: from mail-pd0-f182.google.com ([209.85.192.182]:54522 "EHLO mail-pd0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753143Ab3JPB6i (ORCPT ); Tue, 15 Oct 2013 21:58:38 -0400 Message-ID: <525DF2CA.1060102@gmail.com> Date: Tue, 15 Oct 2013 19:58:34 -0600 From: David Ahern User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:24.0) Gecko/20100101 Thunderbird/24.0.1 MIME-Version: 1.0 To: Namhyung Kim CC: acme@ghostprotocols.net, linux-kernel@vger.kernel.org, Ingo Molnar , Frederic Weisbecker , Peter Zijlstra , Jiri Olsa , Mike Galbraith , Stephane Eranian Subject: Re: [PATCH] perf record: mmap output file - v2 References: <1381805731-10398-1-git-send-email-dsahern@gmail.com> <87txgj9eir.fsf@sejong.aot.lge.com> <525D44B9.7060901@gmail.com> <87haci9e31.fsf@sejong.aot.lge.com> In-Reply-To: <87haci9e31.fsf@sejong.aot.lge.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/15/13 7:52 PM, Namhyung Kim wrote: > Aha, okay. So it mostly matters to syscall tracing, right? For a > normal record session, it seems that the effect is not that large: Yes, that's in the description "When recording raw_syscalls for the entire system" There is a small benefit to all record sessions -- mmap+memcpy has less overhead than write(). I still need to look at Ingo's suggestion to use non-temporal stores which might reduce the overhead of the memcpy. Try a workload that generates a HUGE data file -- say a full kernel build (e.g., perf record -g -- make O=/tmp/kbuild -j 16). You should see a much larger benefit from the mmap route. Be sure to use your callchain enhancements to look at that 1+G file. ;-) David