On Tue, Jan 25, 2011 at 09:44:45AM +0800, Nick Piggin wrote: > On Tue, Jan 25, 2011 at 12:34 PM, Shaohua Li <shaohua.li@xxxxxxxxx> wrote: > > 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@xxxxxxxxx> 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@xxxxxxxxx> 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 against data of > >> >> > the disks. According to perf, we saw more lock contentions: > >> >> > In 2.6.37: 13.00% dbench [kernel.kallsyms] [k] _raw_spin_lock > >> >> > In 2.6.38-rc: 69.45% dbench [kernel.kallsyms] [k]_raw_spin_lock > >> >> > - 69.45% dbench [kernel.kallsyms] [k] _raw_spin_lock > >> >> > - _raw_spin_lock > >> >> > - 48.41% dput > >> >> > - 61.17% path_put > >> >> > - 60.47% do_path_lookup > >> >> > + 53.18% user_path_at > >> >> > + 42.13% do_filp_open > >> >> > + 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. Sure, I'm still at office tomorrow. I can test before that day, otherwise maybe Tim can help. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
