On Fri, Aug 06, 2010 at 01:44:11PM -0500, Steven Pratt wrote: > Here is the latest set of performance runs from the 2.6.35-rc5 tree. > Included is a refresh of all the other filesystems with some changes > for barriers on and off since this has been somewhat of a hot topic > recently. > > New data linked in to the history graphs here: > http://btrfs.boxacle.net/repository/raid/history/History.html > > From a BTRFS performance perspective, we took a major regression on > write heavy workloads. As much as a 10x hit! The problems seems to > be due to this changeset: > http://git.kernel.org/?p=linux/kernel/git/mason/btrfs-unstable.git;a=commit;h=5da9d01b66458b180a6bee0e637a1d0a3effc622
Ouch! The problem is we're not being aggressive enough about allocating chunks for data, which makes the flusher come in and start data IO. Thanks a lot for finding the regression, my machine definitely didn't show this. I'll reproduce and fix it up. -chris > Btrfs: Shrink delay allocated space in a synchronized > > Shrink delayed allocation space in a synchronized manner is more > controllable than flushing all delay allocated space in an async > thread. > > This changeset introduced "btrfs_start_one_delalloc_inode" in > http://git.kernel.org/?p=linux/kernel/git/mason/btrfs-unstable.git;a=commitdiff;h=5da9d01b66458b180a6bee0e637a1d0a3effc622 > > In heavy write workloads this new function is now dominating the profiles: > > samples % app name symbol name > 8914973 65.1261 btrfs.ko btrfs_start_one_delalloc_inode > 1024841 7.4867 vmlinux-2.6.35-rc5-autokern1 rb_get_reader_page > 716046 5.2309 vmlinux-2.6.35-rc5-autokern1 ring_buffer_consume > 315354 2.3037 oprofile.ko add_event_entry > 202484 1.4792 vmlinux-2.6.35-rc5-autokern1 write_inode_now > 195018 1.4247 btrfs.ko btrfs_tree_lock > > > Appears to be major contention on the spin lock, as this gets worse > with more threads. This needs to be redone. > > > Steve > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
