From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shaohua Li Subject: Re: more dput lock contentions in 2.6.38-rc? Date: Tue, 25 Jan 2011 10:01:23 +0800 Message-ID: <20110125020123.GA30965@sli10-conroe.sh.intel.com> References: <1295915725.1949.967.camel@sli10-conroe> <1295917864.1949.970.camel@sli10-conroe> <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" , lkml , Andrew Morton , Nick Piggin , "Chen, Tim C" To: Nick Piggin Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Tue, Jan 25, 2011 at 09:44:45AM +0800, Nick Piggin wrote: > On Tue, Jan 25, 2011 at 12:34 PM, Shaohua Li w= rote: > > On Tue, 2011-01-25 at 09:26 +0800, Nick Piggin wrote: > >> On Tue, Jan 25, 2011 at 12:11 PM, Shaohua Li wrote: > >> > On Tue, 2011-01-25 at 09:04 +0800, Nick Piggin wrote: > >> >> On Tue, Jan 25, 2011 at 11:35 AM, Shaohua Li wrote: > >> >> > Hi, > >> >> > we are testing dbench benchmark and see big drop of 2.6.38-rc= compared > >> >> > to 2.6.37 in several machines with 2 sockets or 4 sockets. We= have 12 > >> >> > disks mount to /mnt/stp/dbenchdata/sd*/ and dbench runs again= st 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.kallsym= s] =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 ext= 3 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. >=20 > 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, thoug= h. Sure, I'm still at office tomorrow. I can test before that day, otherwi= se maybe Tim can help.