Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757678Ab3JQP7d (ORCPT ); Thu, 17 Oct 2013 11:59:33 -0400 Received: from mail-pd0-f178.google.com ([209.85.192.178]:51441 "EHLO mail-pd0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757633Ab3JQP7b (ORCPT ); Thu, 17 Oct 2013 11:59:31 -0400 Message-ID: <52600960.1090907@gmail.com> Date: Thu, 17 Oct 2013 09:59:28 -0600 From: David Ahern User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:24.0) Gecko/20100101 Thunderbird/24.0.1 MIME-Version: 1.0 To: Stephane Eranian CC: LKML , "mingo@elte.hu" , Peter Zijlstra , "ak@linux.intel.com" , Jiri Olsa , Arnaldo Carvalho de Melo , Hugh Dickins Subject: Re: [PATCH v2] perf: disable PERF_RECORD_MMAP2 support References: <20131017142839.GA8482@quad> <52600821.9010304@gmail.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1817 Lines: 47 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? David -- 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/