From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753775Ab1HZMNU (ORCPT ); Fri, 26 Aug 2011 08:13:20 -0400 Received: from merlin.infradead.org ([205.233.59.134]:34582 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752789Ab1HZMNS convert rfc822-to-8bit (ORCPT ); Fri, 26 Aug 2011 08:13:18 -0400 Subject: Re: [BUG] perf_event: semantic of PERF_SAMPLE_READ unclear From: Peter Zijlstra To: Stephane Eranian Cc: LKML , mingo@elte.hu, Robert Richter , Vince Weaver Date: Fri, 26 Aug 2011 14:13:01 +0200 In-Reply-To: References: <1314293560.27911.38.camel@twins> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.0.2- Message-ID: <1314360781.11049.2.camel@twins> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-08-26 at 14:02 +0200, Stephane Eranian wrote: > On Thu, Aug 25, 2011 at 7:32 PM, Peter Zijlstra wrote: > > On Thu, 2011-08-25 at 19:19 +0200, Stephane Eranian wrote: > >> But the difficulty is that > >> we cannot grab any locks, not sure we need one given the call path. > > > > Nah we should be able to simply iterate all siblings and update them > > in-place, since its group members they should all be co-scheduled. The > > only difficulty is cross pmu group members.. > > > Are we allowing event from different PMU to be in the same event group? > If so, is that useful? We allow software events, which can always be scheduled, to be part of a hardware group. We don't allow mixing of different hardware pmus. Allowing a software event is useful if for example the hardware pmu doesn't have a sampling interrupt.