Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757994Ab3JQQJx (ORCPT ); Thu, 17 Oct 2013 12:09:53 -0400 Received: from mail-ob0-f169.google.com ([209.85.214.169]:51529 "EHLO mail-ob0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757077Ab3JQQJw (ORCPT ); Thu, 17 Oct 2013 12:09:52 -0400 MIME-Version: 1.0 In-Reply-To: <52600960.1090907@gmail.com> References: <20131017142839.GA8482@quad> <52600821.9010304@gmail.com> <52600960.1090907@gmail.com> Date: Thu, 17 Oct 2013 18:09:47 +0200 Message-ID: Subject: Re: [PATCH v2] perf: disable PERF_RECORD_MMAP2 support From: Stephane Eranian To: David Ahern Cc: LKML , "mingo@elte.hu" , Peter Zijlstra , "ak@linux.intel.com" , Jiri Olsa , Arnaldo Carvalho de Melo , Hugh Dickins Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1962 Lines: 52 On Thu, Oct 17, 2013 at 5:59 PM, David Ahern wrote: > On 10/17/13 9:57 AM, Stephane Eranian wrote: >> >> On Thu, Oct 17, 2013 at 5:54 PM, David Ahern wrote: >>> >>> On 10/17/13 8:28 AM, Stephane Eranian wrote: >>>> >>>> >>>> >>>> For now, we disable the extended MMAP record support (MMAP2). >>>> We have identified cases where it would not report the correct >>>> mapping information, clone(VM_CLONE) but with separate pids. >>>> We will revisit the support once we find a solution for this case. >>>> >>>> The patch changes the kernel to return EINVAL if attr->mmap2 >>>> is set. The patch also modifies the perf tool to use regular >>>> PERF_RECORD_MMAP >>>> for synthetic events and it also prevents the tool from requesting >>>> attr->mmap2 >>>> mode because the kernel would reject it. >>>> >>>> The support will be revisited once the kenrel interface is updated. >>> >>> >>> >>> Why not disable mmap2 as well: >>> >>> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c >>> index 0ce9febf1ba0..289f34dbe970 100644 >>> --- a/tools/perf/util/evsel.c >>> +++ b/tools/perf/util/evsel.c >>> @@ -678,7 +678,7 @@ void perf_evsel__config(struct perf_evsel *evsel, >>> attr->sample_type |= PERF_SAMPLE_WEIGHT; >>> >>> attr->mmap = track; >>> - attr->mmap2 = track && !perf_missing_features.mmap2; >>> + /* attr->mmap2 = track && !perf_missing_features.mmap2; */ >>> attr->comm = track; >>> >> It is disabled automatically later on. I checked that. Wanted to minimize >> the changes. >> > > Understood that the fallback kicks in. Why fail the perf_event_open every > single time when we know it is not going to succeed? > Ok, I can add that. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/