From mboxrd@z Thu Jan 1 00:00:00 1970 From: Namhyung Kim Subject: Re: Queries on using PERF tool Date: Thu, 29 Nov 2012 23:47:06 +0900 Message-ID: <1354200426.1630.30.camel@leonhard> References: <50B5A903.5080003@core.kaist.ac.kr> <87lidkq4gg.fsf@sejong.aot.lge.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-pb0-f46.google.com ([209.85.160.46]:45508 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752277Ab2K2OrM (ORCPT ); Thu, 29 Nov 2012 09:47:12 -0500 Received: by mail-pb0-f46.google.com with SMTP id wy7so10600829pbc.19 for ; Thu, 29 Nov 2012 06:47:11 -0800 (PST) In-Reply-To: Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Shahina Rabbani Cc: Chulmin Kim , linux-perf-users@vger.kernel.org Hi Shahina, 2012-11-29 (=EB=AA=A9), 13:45 +0530, Shahina Rabbani: > Hi Namhyung Kim , >=20 >=20 > First of all Thanks for your mail. > I have some more doubts. Please help me. >=20 >=20 > Q1: when we are working with more than one CPU, there will be a share= d > L2 cache for all the CPUs and each CPU will have its own L1-cache > If i want to monitor a event and i am using L1-cahce and > L2-caches from CPU1 and the same time if CPU2 is also trying to > monotora particular event and using L2- =20 > cache. Then how the perf tool handles this situation. On a recent kernel and Intel cpus, it supports offcore and/or uncore events for that purpose AFAIK. Please check your cpu manuals. >=20 >=20 > Q2. Can you please list what are the architechtures it is supporting > at present. >=20 >=20 > Q3. Consider the case of Distributed systems, where the processors > are connected through the network and say i am trying to transmit dat= a > over the TCP/IP stack. Is it=20 > possible to monitor the data send at our end and data receive= d > from the other end using the perf tool?? The perf tools work with pipe so that we might use nc/netcat for this. Only tested on a local machine: $ nc -l localhost 8282 | perf report -i - $ perf record -o - sleep 1 | nc localhost 8282 >=20 >=20 > Q4. when using perf record. Say i have got the data in perf.data file= =2E > Say i am using this file to get some information and assume that > system crashes and the perf.data file is=20 > in inconsistent state. when u reboot the system after the crash= , > is it posssible to get the perf.data file safely.??? I doubt you can use the file safely. There's no guarantee when system crashed. Thanks, Namhyung >=20 >=20 > Q5. Say i am counting some samples depending on the clock. and assume > that i change the clock in between., Then the perf tool will be able > to understand the situation and count the samples depending on the ol= d > and ne changed clocks or do we need to provide this information to > perf tool.?? how to handle this situation??