ZFS v15 slowness

[Martin Matuska]

 To my experience, processes spend more time in zio (as of top).

When there is a lot of FS activity the system responsiveness goes down
(filesystem reacts slowly or gets stallish).
A good example is my tinderbox system - when tinderbox does a lot of
small ports (heavy ZFS activity, untarring of many files and compiling,
searching for changed files, etc.) the system shows a stallish behaviour
in disk reads and my shell reacts slowly. With the stat and rrwlock
patch it responds slightly better as it did before v15. The question is,
why.

The affected system is core i7, amd64, 8GB ram, 2x750GB sata2 drives in
a ZFS mirror.
vm.kmem_size="6G"
vfs.zfs.arc_max="4G"

Anyway, I would vote for these patches, maybe including ABE (it doesn't
hurt).

Dňa 23. 7. 2010 11:17, Pawel Jakub Dawidek  wrote / napísal(a):
> On Fri, Jul 23, 2010 at 09:35:00AM +0200, Martin Matuska wrote:
>>  Hi Pawel and Xin,
>>
>> I have a user report and I can confirm myself of ZFS v15 acting slower
>> than before the import on several systems.
>> I would therefore like to propose the combined stat() and rrwlock
>> speedup patch as this has noticeable impact on this issue in my tests
>> and the overall impression of system responsiveness.
> Of course speed up is very welcome, but as I read it v15 is slower than
> v14 for some unknown reason. So of course getting more optimizations is
> desirable, but not really related to why v15 is slower than v14.
> Is my understanding correct? What kind of performance problems do you
> observe?
>