On 07/02/2012 01:44 PM, Jan Kara wrote:
On Mon 02-07-12 11:33:33, Eric Sandeen wrote:
On 07/01/2012 10:16 PM, Zheng Liu wrote:
Hi Eric,
Could you please run this test with 'journal_async_commit' flag. In my
previous test, this feature can dramatically improve the performance of
uninitialized extent conversion.
I have sent an email to do a similar test [1]. In that email, I do a
similar test and the journal_async_commit flag quite can improve the
performance.
I can try to find time for that, but so far I haven't actually seen any
severe impact of conversion on a non-debug kernel. And didn't Jan think
that journal_async_commit was fatally flawed?
Yes, that option is broken and basically unfixable for data=ordered mode
(see http://comments.gmane.org/gmane.comp.file-systems.ext4/30727). For
data=writeback it works fine AFAICT.
Honza
I think that we need to start with the basics - let's find a specific work load
that we can use to validate the performance. In Eric's testing, nothing really
jumped out.
What type of disk, the specific worst case IO size, etc would be great (and even
better, if someone has a real world, non-synthetic app that shows this).
Definitely more interesting I think to try and do the MB size extent conversion,
that should be generally a good technique to minimize the overhead.
thanks!
Ric
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