ZFS v15 slowness

[Pawel Jakub Dawidek]

On Fri, Jul 23, 2010 at 12:47:13PM +0200, Martin Matuska wrote:
>  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. [...]

This looks like priority problem. What kernel threads consume most CPU
time when if feel slowdown? Do you have compression enabled on loaded
datasets? I'd try lowering priority of the guilty thread and see what
happen.

> [...] 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).

I'd prefer to address performance problem with v15 first and then merge
stat(2) speed up changes, especially that with stat(2) patch it is
harder to reproduce.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 196 bytes
Desc: not available
Url : http://lists.freebsd.org/pipermail/zfs-devel/attachments/20100724/abb01971/attachment-0001.pgp