A specific example of a disk i/o problem (was: FreeBSD vs Ubuntu)

[Attilio Rao]

2009/9/30 Dieter <freebsd at sopwith.solgatos.com>:
>> > My question is why is FreeBSD's disk i/o performance so bad?
>>
>> As I mentioned... this was discussed actively in slashdot. You will  find
>> there many good comments on this.
>
> All I saw in slashdot was a ffs vs ext comment.  I don't believe the problems
> I'm seeing are filesystem related.
>
>> > Not just in the benchmarks with debugging on, but in real world usage
>> > where it actually matters.
>>
>> Are you saying this from actual experience or from reading other people's
>> comments?
>
> Here is a specific demo of one disk i/o problem I'm seeing.  Should be
> easy to reproduce?
>
> http://lists.freebsd.org/pipermail/freebsd-performance/2008-July/003533.html
>
> This was over a year ago, so add 7.1 to the list of versions with the problem.
> I believe that the
> swap_pager: indefinite wait buffer: bufobj: 0, blkno: 1148109, size: 4096
> messages I'm getting are the same problem.  A user process is hogging
> the bottleneck (disk buffer cache?) and the swapper/pager is getting starved.

Sorry, do you have a PR/describing e-mail with this issue? Can you be
a bit more precise?

The problem reported in the earlier post, however, is interesting and
worths more analysis.
More speficially, would you be interested in reproducing and playing a
bit with some diagnostic tool/configurations I can point you at?

Attilio


-- 
Peace can only be achieved by understanding - A. Einstein