From mboxrd@z Thu Jan 1 00:00:00 1970 From: Namhyung Kim Subject: Re: perf sched record with -p option Date: Thu, 8 Feb 2018 14:07:08 +0900 Message-ID: <20180208050708.GC24686@sejong> References: <30C2D590D16A5C46ADFE65219103779892616691@AZ-US1EXMB02.global.avaya.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Received: from LGEAMRELO11.lge.com ([156.147.23.51]:45483 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750711AbeBHFHR (ORCPT ); Thu, 8 Feb 2018 00:07:17 -0500 Content-Disposition: inline In-Reply-To: <30C2D590D16A5C46ADFE65219103779892616691@AZ-US1EXMB02.global.avaya.com> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: "Vuille, Martin (Martin)" Cc: "linux-perf-users@vger.kernel.org" , kernel-team@lge.com Hello, On Sun, Feb 04, 2018 at 05:31:07PM +0000, Vuille, Martin (Martin) wrote: > The data files collected by 'perf sched record' are very large and our embedded > system target has limited storage, so I thought of using the '-p PID' option on > 'perf sched record' to focus only on a single PID and its threads/children and > thus reduce the amount of data. > > However, when I review the results with 'perf sched latency', the results from > data collected with '-p PID' are significantly different (e.g., ten-times longer > latencies) that those from data collected without the '-p PID' option. Workloads > are the same. > > Is there some reason why using '-p PID' option on 'perf sched record' wouldn't > make sense? I think it's because perf missed sched-in and wakeup events for the PID since they are from different tasks. Thanks, Namhyung