Possible evidence of performance regression for 8.1-S (vs. 7.1)

David Wolfskill david at catwhisker.org
Wed Oct 27 11:19:05 UTC 2010

On Wed, Oct 27, 2010 at 01:06:18PM +0200, Ivan Voras wrote:
> On 10/27/10 12:55, David Wolfskill wrote:
> > That *is* a problem, as I cannot justify a migration to a branch
> > of FreeBSD that imposes about a 23% penalty in elapsed time on this
> > workload.  I want folks at work to have more reason to want to use
> > (newer branches of) FreeBSD, not less.
> That is understandable,


> I'm only saying that given the symptoms - some
> "waiting" that is not accounted in system or user time and with NFS
> mostly ruled out (maybe a better test would be to extract a local
> tarball *to* the NFS server),

I could run that test, sure....

> the next suspect is the disk system. In
> case you never tried "diskinfo -vt", its results look like this:
> 	outside:       102400 kbytes in   1.222998 sec =    83729 kbytes/sec
> 	middle:        102400 kbytes in   1.448580 sec =    70690 kbytes/sec
> 	inside:        102400 kbytes in   2.531694 sec =    40447 kbytes/sec
> note 2x drop in performance between outer and inner tracks.

OK, but I'm not sure how that's likely to work for a multi-spindle RAID
0 group....

> It's not
> certain, especially since your results are repeatable and you always use
> exactly the same file system,

For the NFS tests just done.  For the "real" tests, the same file system
was used when I ran the tests on the same machine; (obviously) different
machines have different (local) file systems.  (Still, similarly-
configured 4-spindle RAID 0 groups were used for the target file
systems on each machine.)

> but it's possible. Have you tried the sysctls I've posted?

Err... Not yet, no.  I just got up & read your message.  I leave for
work in just over 3 hours.  :-}  [While it is possible to login from
home, it's a liitle more awkward than (say) logging in to the FreeBSD
cluster, and this is the time of day when I reboot my laptop a few times
-- it's presently running  9.0-CURRENT #23 r214372 & building
9.0-CURRENT #23 r214413; it just finished building & smoke-testing
FreeBSD 8.1-STABLE #14 r214413.]

David H. Wolfskill				david at catwhisker.org
Depriving a girl or boy of an opportunity for education is evil.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.
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