From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751648Ab0IFLyS (ORCPT ); Mon, 6 Sep 2010 07:54:18 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:43900 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750784Ab0IFLyR convert rfc822-to-8bit (ORCPT ); Mon, 6 Sep 2010 07:54:17 -0400 Subject: Re: disabling group leader perf_event From: Peter Zijlstra To: Avi Kivity Cc: linux-perf-users@vger.kernel.org, linux-kernel , Ingo Molnar In-Reply-To: <4C84D1CE.3070205@redhat.com> References: <4C84B088.5050003@redhat.com> <1283772256.1930.303.camel@laptop> <4C84D1CE.3070205@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Mon, 06 Sep 2010 13:54:05 +0200 Message-ID: <1283774045.1930.341.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2010-09-06 at 14:34 +0300, Avi Kivity wrote: > On 09/06/2010 02:24 PM, Peter Zijlstra wrote: > > On Mon, 2010-09-06 at 12:12 +0300, Avi Kivity wrote: > >> If I read the code correctly, disabling a group leader perf_event will > >> disable the entire group. > >> > >> Is this correct? > > Yeah, pretty much. > > Well, I never liked group_leader style APIs. I like different types for > the container and the contained. But such is not unix. > > >> If so, how can I disable just the event itself? Can I allocate a dummy > >> invent for the group leader so I can enable and disable each perf_event > >> in the group individually? > > Which makes me wonder why you use groups in the first place. > > Basically, to read() all events in one go. I have many of them. > > My current problem is that I have an event (kvm_exit) which I want to > drill down by looking at a field (exit_reason). So I create lots of > separate perf_events with a filter for each reason: > kvm_exit(exit_reason==0), kvm_exit(exit_reason==1), etc. But filters > are fairly slow (can have ~60 such events on AMD), so I want to make > this drill-down optional. Yeah, filters suck. So what you're basically trying to do is create some histogram of exit_reason? Being able to make histograms in-kernel has been on the todo list for a long while, its just that I never could come up with a sane interface.. :/ > Current plan is to have a group for the basic events and another group > for the drilldown events (each per-cpu), and activate the drilldown > group on user request. perf will be able to schedule both groups > concurrently since they only contain tracepoints, yes? More or less, yeah (the scheduling of software and hardware events isn't properly separated atm -- am working on that). Software events have no scheduling constraints and should always get scheduled.