On Fri, 2009-03-27 at 16:24 -0400, Theodore Ts'o wrote:
> The following patches have been posted as providing at least some
> partial improvement to the ext3 latency problem that has been
> discussed on the 2.6.29 mongo-LKML-thread-that-would-not-die.

Ric had asked me about a test program that would show the worst case
ext3 behavior.  So I've modified your ext3 program a little.  It now
creates a 8G file and forks off another proc to do random IO to that
file.

Then it runs one fsync every 4 seconds and times how long they take.
After the program has been running for 60 seconds, it tries to stop.

On my sata drive with barriers on, even btrfs and xfs saw some
multi-second fsyncs, but ext3 came in at 414s for a single fsync.

Warning: don't run this on a laptop drive, you'll still be waiting for
it next year.  This is probably full of little errors, I cut it together
pretty quickly.

-chris