From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756749Ab0ECUxY (ORCPT ); Mon, 3 May 2010 16:53:24 -0400 Received: from smtp-out.google.com ([216.239.44.51]:21657 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754921Ab0ECUxW (ORCPT ); Mon, 3 May 2010 16:53:22 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=mime-version:in-reply-to:references:date:message-id:subject:from:to: cc:content-type:x-system-of-record; b=fJbPgAOXvUMEcAXdmlx/VR96LuHehCpI266zMa8rsfmmc27YEXVEhRqNJa2v2YlEh 1OkqrmsqEKgsh8tHkwMgA== MIME-Version: 1.0 In-Reply-To: <1272919356.1642.154.camel@laptop> References: <20100503203813.GA17886@sharma-home.net> <1272919356.1642.154.camel@laptop> Date: Mon, 3 May 2010 13:53:19 -0700 Message-ID: Subject: Re: [PATCH] perf: implement recording/reporting per-cpu samples From: Arun Sharma To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, paulus@samba.org, davem@davemloft.net, fweisbec@gmail.com Content-Type: text/plain; charset=UTF-8 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 3, 2010 at 1:42 PM, Peter Zijlstra wrote: > > On Mon, 2010-05-03 at 13:38 -0700, Arun Sharma wrote: > > Enable PERF_SAMPLE_CPU by default. Implement --sort cpu. > > Why? The downside is that you unconditionally grow each sample and thus > increase the overhead for something that doesn't make sense for the > normal (task-inherit) case. In a shared multi-core environment, users want to analyze why their program was slow. In particular, if the code ran slower only on certain CPUs due to interference from other programs or kernel threads, they want to know that. But that's just our use case. The patch is mostly about --sort cpu option. If you want to drop the part that enables PERF_SAMPLE_CPU by default, that's fine by me. -Arun