Return-Path: <linux-kernel-owner+w=401wt.eu-S1753551AbZGAHb6@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753551AbZGAHb6 (ORCPT <rfc822;w@1wt.eu>);
	Wed, 1 Jul 2009 03:31:58 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752854AbZGAHbu
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Wed, 1 Jul 2009 03:31:50 -0400
Received: from mx3.mail.elte.hu ([157.181.1.138]:44538 "EHLO mx3.mail.elte.hu"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751212AbZGAHbu (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Wed, 1 Jul 2009 03:31:50 -0400
Date: Wed, 1 Jul 2009 09:31:39 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Paul Mackerras <paulus@samba.org>,
       =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH][RFC] Adding information of counts processes acquired
	how many spinlocks to schedstat
Message-ID: <20090701073139.GA12073@elte.hu>
References: <20090701.152115.706994265076015808.mitake@dcl.info.waseda.ac.jp>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20090701.152115.706994265076015808.mitake@dcl.info.waseda.ac.jp>
User-Agent: Mutt/1.5.18 (2008-05-17)
X-ELTE-SpamScore: -1.5
X-ELTE-SpamLevel: 
X-ELTE-SpamCheck: no
X-ELTE-SpamVersion: ELTE 2.0 
X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5
	-1.5 BAYES_00               BODY: Bayesian spam probability is 0 to 1%
	[score: 0.0000]
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2565
Lines: 78


* Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> wrote:

> Hi,
> 
> I wrote a test patch which add information of counts processes 
> acquired how many spinlocks to schedstat. After applied this 
> patch, /proc/<PID>/sched will change like this,
> 
> init (1, #threads: 1)
> ---------------------------------------------------------
> se.exec_start                      :        482130.851458
> se.vruntime                        :         26883.107980
> se.sum_exec_runtime                :          2316.651816
> se.avg_overlap                     :             0.480053
> se.avg_wakeup                      :            14.999993
> ....
> se.nr_wakeups_passive              :                    1
> se.nr_wakeups_idle                 :                    0
> se.nr_acquired_spinlock            :                74483
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Looks potentially useful - but it would be nice and go one step 
further and add lock acquire stats as a software-counter.

Perfcounters is a feature of the latest upstream kernel, there's a 
(still very small) Wiki page about it at:

   http://perf.wiki.kernel.org

With perfcounters we can instrument various software properties of 
the kernel as well, for example the number of page-faults in the 
system per second:

  $ perf stat -a -e page-faults sleep 1

  Performance counter stats for 'sleep 1':

          294387  page-faults             

     1.022318527  seconds time elapsed

Now, it would be nice to have a lock-acquire software-counter as 
well, which would output things like:

  $ perf stat -a -e lock-acquires sleep 1

  Performance counter stats for 'sleep 1':

          294387  lock-acquires

     1.022318527  seconds time elapsed

Furthermore, beyond plain counts, doing this would also allow the 
profiling of lock acquire places: perf record -e lock-acquires and 
perf report would work fine.

It is really easy to add a new sw counter, check how it is done for 
the pagefault counter(s), see the uses of PERF_COUNT_SW_PAGE_FAULTS 
in the following files:

  $ git grep -l PERF_COUNT_SW_PAGE_FAULTS

  arch/powerpc/mm/fault.c
  arch/x86/mm/fault.c
  include/linux/perf_counter.h
  kernel/perf_counter.c
  tools/perf/builtin-stat.c
  tools/perf/design.txt

Would you be interested in having a look at this?

	Ingo
--
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/