From mboxrd@z Thu Jan  1 00:00:00 1970
From: Nick Piggin <npiggin@gmail.com>
Subject: Re: more dput lock contentions in 2.6.38-rc?
Date: Tue, 25 Jan 2011 12:44:45 +1100
Message-ID: <AANLkTikfxGF_4ZjJXP7kNChkDBnva5iStTPRLs3B86+c@mail.gmail.com>
References: <1295915725.1949.967.camel@sli10-conroe>
	<AANLkTikOdiQR+rWXzoU9z5sJv9Q2=ehdhi1NCHXT0a-w@mail.gmail.com>
	<1295917864.1949.970.camel@sli10-conroe>
	<AANLkTimwSNsjR5PnVP8JvzwEBwy3VtDp4DvNecKsTnxJ@mail.gmail.com>
	<1295919258.1949.973.camel@sli10-conroe>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: QUOTED-PRINTABLE
Cc: "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Nick Piggin <npiggin@kernel.dk>,
	"Chen, Tim C" <tim.c.chen@intel.com>
To: Shaohua Li <shaohua.li@intel.com>
Return-path: <linux-fsdevel-owner@vger.kernel.org>
Received: from mail-wy0-f174.google.com ([74.125.82.174]:58720 "EHLO
	mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751529Ab1AYBor convert rfc822-to-8bit (ORCPT
	<rfc822;linux-fsdevel@vger.kernel.org>);
	Mon, 24 Jan 2011 20:44:47 -0500
In-Reply-To: <1295919258.1949.973.camel@sli10-conroe>
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

On Tue, Jan 25, 2011 at 12:34 PM, Shaohua Li <shaohua.li@intel.com> wro=
te:
> On Tue, 2011-01-25 at 09:26 +0800, Nick Piggin wrote:
>> On Tue, Jan 25, 2011 at 12:11 PM, Shaohua Li <shaohua.li@intel.com> =
wrote:
>> > On Tue, 2011-01-25 at 09:04 +0800, Nick Piggin wrote:
>> >> On Tue, Jan 25, 2011 at 11:35 AM, Shaohua Li <shaohua.li@intel.co=
m> wrote:
>> >> > Hi,
>> >> > we are testing dbench benchmark and see big drop of 2.6.38-rc c=
ompared
>> >> > to 2.6.37 in several machines with 2 sockets or 4 sockets. We h=
ave 12
>> >> > disks mount to /mnt/stp/dbenchdata/sd*/ and dbench runs against=
 data of
>> >> > the disks. According to perf, we saw more lock contentions:
>> >> > In 2.6.37: 13.00% =A0 =A0 =A0 =A0dbench =A0[kernel.kallsyms] =A0=
 [k] _raw_spin_lock
>> >> > In 2.6.38-rc: 69.45% =A0 =A0 =A0 =A0dbench =A0[kernel.kallsyms]=
 =A0 [k]_raw_spin_lock
>> >> > - =A0 =A0 69.45% =A0 =A0 =A0 =A0dbench =A0[kernel.kallsyms] =A0=
 [k] _raw_spin_lock
>> >> > =A0 - _raw_spin_lock
>> >> > =A0 =A0 =A0- 48.41% dput
>> >> > =A0 =A0 =A0 =A0 - 61.17% path_put
>> >> > =A0 =A0 =A0 =A0 =A0 =A0- 60.47% do_path_lookup
>> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 + 53.18% user_path_at
>> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 + 42.13% do_filp_open
>> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 + 4.69% user_path_parent
>> >>
>> >> What filesystems are mounted on the path?
>> > ext3 or ext4
>>
>> ext3 or 4 along every step of the path? Are there
>> any acls loaded, or security policy running?
> all disks are formated with the same fs, just some machines use ext3 =
and
> others ext4. no we don't have acl or security policy.
>> It may be possible that they're all coming from
>> /proc/ access.
> I added trace in dput just after the lock taken. and most files are '=
/',
> 'mnt', 'stp'. the percentage of 'proc' is small actually.

Hm, OK well I could send you a patch to gather some statistics for
why rcu-walk gets dropped. It'll have to wait until I get home, though.
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel=
" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html