On Thu, Jun 02, 2011 at 10:36:33AM -0400, Vivek Goyal wrote: > On Thu, Jun 02, 2011 at 10:17:16AM -0400, Vivek Goyal wrote: > > On Thu, Jun 02, 2011 at 11:22:09AM +1000, Dave Chinner wrote: > > > On Wed, Jun 01, 2011 at 05:50:49PM -0400, Vivek Goyal wrote: > > > > Hi, > > > > > > > > If I throttle a DIO/AIO WRITE bio at block device in a cgroup, will it > > > > lead to any kind of serialization of ext4 file system. IOW, is there any > > > > filesystem operation which will wait for that DIO/AIO WRITE to finish > > > > before other filesystem can make progress (fsync, journalling etc?) > > > > > > Truncate? > > > > > > (XFS explicitly serialises truncate against in flight DIO, > > > regardless of whether ext4 does.) > > > > > > > Dave, > > > > Does this serialization happens against that particular inode on which > > truncate has been called? If yes, then I think I will still be fine > > as in common use case I am not expecting much sharing of inodes across > > cgroups. > > Dave, > > I did a quick test of throttling a direct IO on one file and then > doing "truncate -s 40 testfile" on a different file in different > cgroup and it seems to work fine. > > But I seem to be having issues with "sync". Looks like in ext4, if > I throttle a DIO, sync does not hang but in XFS it does. I am > wondering if XFS is waiting for all inflight DIO to finish before > sync completes. "sync" on XFS seems to be livelocking as long as DIO write operation is going on and same does not happen on ext4. I ran "aio-stress -O aiofile1 -s 4G" and in other window I did "sync" and it does not finish untile and unless aio-stress has finished. On the other hand ext4 seems to be fine and it does finish earlier. Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
