On Mon, 21 Dec 1998, Robert M. Hyatt wrote:
>
> I am testing this on my quad xeon, and it does look better. IE a compute
> bound process seems to stick on one cpu for long periods of time. It will
> occasionally move, when the process does an I/O, but it is far better than
> it was, in that running xosview would show a single process bouncing
> around quite frequently...
Umm.. What about interactive feel?
PLEASE PLEASE PLEASE don't think that "stick to one CPU" is automatically
a good thing. It isn't. It has absolutely no meaning what-so-ever aside
from cache issues, and can be an extremely _bad_ thing for other reasons.
One of the other reasons is interactive performance and scheduling latency
under load.
Any patches that are developed using xosview and looking at the load meter
are very very suspect. PLEAE don't do that, it is a completely bogus
metric.
The only thing that matters is:
- absolute performance (ie NUMBERS, not "xosview says it sticks to a
CPU")
- latency and responsiveness.
And note that the second one is MORE important - I'd much rather have a
machine that feels good than one that benchmarks 5% better.
If the only criterion is how xosview looks, then I don't want to see the
patches, quite frankly. Nice "sticks to one CPU" behaviour on osview does
NOT automatically mean that performance is actually better, and it can
easily mean that interactive response is pure crap.
Note that if you have a quad PII, interactive response is usually fine -
and the cross-CPU scheduling stuff doesn't matter unless you have a
CPU-bound load noticeably over four. Be very very careful.
Linus
-
Linux SMP list: FIRST see FAQ at http://www.irisa.fr/prive/mentre/smp-faq/
To Unsubscribe: send "unsubscribe linux-smp" to [EMAIL PROTECTED]
