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? It may be possible that they're all coming from /proc/ access. > >> > - 35.56% d_path >> > seq_path >> > show_vfsmnt >> > seq_read >> > vfs_read >> > sys_read >> > system_call_fastpath >> > __GI___libc_read >> >> This guy is from glibc's statvfs call that dbench uses. It >> parses /proc/mounts for mount flags which is racy (and >> not a good idea to do with any frequency). >> >> A patch went into the kernel that allows glibc to get the >> flags directly. Not sure about glibc status, I imagine it >> will get there in another decade or two... Can you try >> commenting it out of dbench source code? > Sure, maybe after Chinese new year holiday, sorry. No problem. Thanks, Nick -- 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
