Re: Performance of ext4

[Eric Sandeen <sandeen@redhat.com>]

Theodore Tso wrote:
> On Tue, Jun 17, 2008 at 11:42:36AM +0000, Holger Kiehl wrote:
>> Note how the size of file results.24033.helena.dwd.de changes from
>> 9230 before the test to 8208 bytes after the test. Also note the
>> date both have the same timestamp "2008-06-17 04:35". I have made a
>> copy of results.24033.helena.dwd.de before the test and compared it
>> with that after the test. The file is just truncated by 1022 bytes
>> and there is no garbage.
> 
> So the corruption is always a truncation, correct?
> 
> Did you notice the problem with ext4 w/o the patch queue?  I have a
> suspicion that the problem may have been introduced by the delayed
> allocation code, but I don't have hard evidence.  When you rerun your
> benchmark (which seems to be the closest thing we have to a
> reproduction case), it would be interesting to know if the problem
> goes away with -o nodelalloc (again, it would localize where we need
> to look).
> 
> Thanks, regards,

It might be worth runninga "simple" fsx under your kernel too; last time
I tested fsx it was still happy and it exercises fs ops (including
truncate) at random...

-Eric