On Tue, Jan 25, 2011 at 1:01 PM, Shaohua Li <shaohua.li@xxxxxxxxx> wrote: > 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. There _are_ a lot of dput contentions coming from d_path. Some of the dentries you're seeing in dput could be coming from path_put in d_path (mountpoints, eg. 'mnt'). What does an actual snippet from perf with callgraphs look like? -- 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
