On Fri, 2009-03-27 at 16:50 -0400, Chris Mason wrote: > 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. > My understanding of ext4 delalloc is that once blocks are allocated to file, we go back to data=ordered. Ext4 is going pretty slowly for this fsync test (slower than ext3), it looks like we're going for a very long time in jbd2_journal_commit_transaction -> write_cache_pages. -chris -- 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
