From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754637AbbDXN6v (ORCPT ); Fri, 24 Apr 2015 09:58:51 -0400 Received: from mail-ig0-f169.google.com ([209.85.213.169]:37206 "EHLO mail-ig0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751741AbbDXN6t (ORCPT ); Fri, 24 Apr 2015 09:58:49 -0400 Message-ID: <553A4C18.3030609@gmail.com> Date: Fri, 24 Apr 2015 07:58:48 -0600 From: David Ahern User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Yunlong Song , a.p.zijlstra@chello.nl, paulus@samba.org, mingo@redhat.com, Arnaldo Carvalho de Melo CC: linux-kernel@vger.kernel.org, wangnan0@huawei.com Subject: Re: [Question] How does perf still record the stack of a specified pid even when that process is interrupted and CPU is scheduled to other process References: <553A45CA.8020808@huawei.com> In-Reply-To: <553A45CA.8020808@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/24/15 7:31 AM, Yunlong Song wrote: > Now we are profiling the performance of ext4 and f2fs on an eMMC card with iozone, > we find a case that ext4 is better than f2fs in random write under the test of > "iozone -s 262144 -r 64 -i 0 -i 2". We want to analyze the I/O delay of the two > file systems. We have got a conclusion that 1% of sys_write takes up 60% time of > the overall sys_write (262144/64=4096). We want to find out the call stack during > this specific 1% sys_write. Our idea is to record the stack in a certain time period > and since the specific 1% case takes up 60% time, the total number of records of its > stack should also takes up 60% of the total records, then we can recognize those stacks > and figure out what the I/O stack of f2fs is doing in the 1% case. And to address this specific profiling problem have you tried: perf trace record -- iozone ... perf trace -i perf.data -S