From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753995Ab3KEI3B (ORCPT ); Tue, 5 Nov 2013 03:29:01 -0500 Received: from mga02.intel.com ([134.134.136.20]:3748 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750943Ab3KEI3A (ORCPT ); Tue, 5 Nov 2013 03:29:00 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.93,535,1378882800"; d="scan'208";a="403767957" Message-ID: <5278AC36.1020702@intel.com> Date: Tue, 05 Nov 2013 10:28:38 +0200 From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Jiri Olsa CC: Arnaldo Carvalho de Melo , Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, David Ahern , Frederic Weisbecker , Mike Galbraith , Namhyung Kim , Paul Mackerras , Stephane Eranian Subject: Re: [PATCH V3 06/11] perf record: Add an option to force per-cpu mmaps References: <1383313899-15987-1-git-send-email-adrian.hunter@intel.com> <1383313899-15987-7-git-send-email-adrian.hunter@intel.com> <20131104152942.GA4004@krava.brq.redhat.com> In-Reply-To: <20131104152942.GA4004@krava.brq.redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/11/13 17:29, Jiri Olsa wrote: > On Fri, Nov 01, 2013 at 03:51:34PM +0200, Adrian Hunter wrote: >> By default, when tasks are specified (i.e. -p, -t >> or -u options) per-thread mmaps are created. Add >> an option to override that and force per-cpu mmaps. >> >> Signed-off-by: Adrian Hunter >> --- >> tools/perf/Documentation/perf-record.txt | 6 ++++++ >> tools/perf/builtin-record.c | 2 ++ >> tools/perf/util/evlist.c | 4 +++- >> tools/perf/util/evsel.c | 4 ++-- >> tools/perf/util/target.h | 1 + >> 5 files changed, 14 insertions(+), 3 deletions(-) >> >> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt >> index f10ab63..2ea6685 100644 >> --- a/tools/perf/Documentation/perf-record.txt >> +++ b/tools/perf/Documentation/perf-record.txt >> @@ -189,6 +189,12 @@ abort events and some memory events in precise mode on modern Intel CPUs. >> --transaction:: >> Record transaction flags for transaction related events. >> >> +--force-per-cpu:: >> +Force the use of per-cpu mmaps. By default, when tasks are specified (i.e. -p, >> +-t or -u options) per-thread mmaps are created. This option overrides that and >> +forces per-cpu mmaps. A side-effect of that is that inheritance is >> +automatically enabled. Add the -i option also to disable inheritance. > > I recently sent out patch that actually force perf cpu mmaps for -p,-t,-u > http://marc.info/?l=linux-kernel&m=138332119912433&w=2 > > Is there a reason why would you want to keep single > mmap (in record command) and cut yourself from inherited > events? Not sure I understand the question. perf supports having a single context for a thread. That is a feature. You seem to be removing perf tools support for it. I image a case where the user has hundreds of CPUs but just wants to record one thread. Currently -t does that. i.e. one file descriptor and one mmap saving megabytes of memory. Another advantage of per-thread mmaps is that you do not need to sample time (nor cpu), because the events are recorded in order. I was adding a feature. Users can choose per-cpu mmaps if they want.