Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932193AbbDYOFu (ORCPT ); Sat, 25 Apr 2015 10:05:50 -0400 Received: from szxga01-in.huawei.com ([58.251.152.64]:34268 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751472AbbDYOFs (ORCPT ); Sat, 25 Apr 2015 10:05:48 -0400 Message-ID: <553B9F30.1040100@huawei.com> Date: Sat, 25 Apr 2015 22:05:36 +0800 From: Yunlong Song User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: David Ahern , , , , Arnaldo Carvalho de Melo CC: , 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> <553A4C18.3030609@gmail.com> In-Reply-To: <553A4C18.3030609@gmail.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.111.74.205] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1368 Lines: 33 On 2015/4/24 21:58, David Ahern wrote: > 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 > > > > But this only shows the system call like strace, but we want the call stack of kernel functions in fact. -- Thanks, Yunlong Song -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/