Re: xfs: very slow after mount, very slow at umount

Dave Chinner
2011-01-27T23:37:40Z

On Wed, Jan 26, 2011 at 10:49:03PM -0500, Mark Lord wrote:
> On 11-01-26 10:30 PM, Dave Chinner wrote:
> > [Please cc xfs@oss.sgi.com on XFS bug reports. Added.]
> >
> > On Wed, Jan 26, 2011 at 08:22:25PM -0500, Mark Lord wrote:
> >> Alex / Christoph,
> >>
> >> My mythtv box here uses XFS on a 2TB drive for storing recordings and videos.
> >> It is behaving rather strangely though, and has gotten worse recently.
> >> Here is what I see happening:
> >>
> >> The drive mounts fine at boot, but the very first attempt to write a new file
> >> to the filesystem suffers from a very very long pause, 30-60 seconds, during which
> >> time the disk activity light is fully "on".
> >
> > Please post the output of xfs_info <mtpt> so we can see what you
> > filesystem configuration is.
>
> /dev/sdb1 on /var/lib/mythtv type xfs
> (rw,noatime,allocsize=64M,logbufs=8,largeio)
>
> [~] xfs_info /var/lib/mythtv
> meta-data=/dev/sdb1 isize=256 agcount=7453, agsize=65536 blks
> = sectsz=512 attr=2
> data = bsize=4096 blocks=488378638, imaxpct=5
> = sunit=0 swidth=0 blks
> naming =version 2 bsize=4096 ascii-ci=0
> log =internal bsize=4096 blocks=32768, version=2
> = sectsz=512 sunit=0 blks, lazy-count=0
> realtime =none extsz=4096 blocks=0, rtextents=0

7453 AGs means that the first write coud cause up to ~7500 disk
reads to occur as the AGF headers are read in to find where the
best free space extent for allocation lies.

That'll be your problem.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com