diskio low read performance

Michel Santos michel at lucenet.com.br
Sat Jan 13 20:03:20 UTC 2007

Kris Kennaway disse na ultima mensagem:
>> But also I checked the ULE/BSD against my particular problem and there
>> is
>> no difference at all. I get no acceptable disk read performance when
>> comparing what I had with 4.11, wether with ULE or with 4BSD
> Be very careful, because I've personally measured severe disk I/O
> penalties with ULE on SMP hardware.  In fact in my testing ULE gives
> worse SMP performance under load across the board compared to 4BSD
> (it's only faster for the lightest of workloads).

seems suspicious and I will compile this night and recheck to be sure

> If you're absolutely certain that ULE is not to blame (and want to
> continue to take the risk of other performance and stability problems
> down the line), that basically leaves something to do with the scsi
> driver and/or its interaction with your hardware as the probable
> cause.  I don't know enough about this particular hardware to comment
> further though.

I will check 4BSD again, but I do not have stability problems. The system
works really constant and without any odds but the diskio thing

certainly the reason why I have a LSI card is that I was blaming the
adaptec driver first, but even with the adaptec disabled and the LSI card
on the Supermicro nothing changed. So I do not know for sure but unlikely
both drivers have the same problem I guess.

> * adaptive mutexes are usually a win so it's a bit unusual that you
> have disabled them, but I assume you have tested this.

I get better network performance when not using polling with it and seems
not to harm polling in my case so I let it in

> * Dunno about the AUTO_EOI_1 option, I don't think you even have this
> hardware on your system (device atpic didn't probe in your dmesg).

right, it is a old setting I ever forget taking it out

> * HZ=1000 is superfluous since it is the default but may or may not
> help.  In some workloads the increased overhead relative to the old
> default of HZ=100 gives a performance loss.  Maybe it helps with
> polling though, I dunno.

that I did not know but does no bad either. With lower HZ it does not work
for me and I have the impression it works better with 2000. I have 5 NICs
and that is the reason I guess. But it is not my priority at this moment
and I believe it does not mess with diskio.


computador é como nem cavalo e mulher
mais que montam neles, pior que ficam ...

Datacenter Matik http://datacenter.matik.com.br
E-Mail e Data Hosting Service para Profissionais.

More information about the freebsd-performance mailing list