On Mon, 21 Dec 1998, Linus Torvalds wrote:
> 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?
I have noticed some 15% increase in x11amp's CPU usage when it
is 'bouncing around' CPUs compared to when it isn't.
Most of this difference is probably cosmetic, but still it helps
a bit when x11amp (running RT) consumes less CPU...
> 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.
Better CPU binding not only takes care of a 'hot cache', it
also leaves more memory bandwidth open for other processors.
I guess that this effect is usually small and DaveM could actually
be the only one able to measure this, but still :))
> 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.
While very very suspect, xosview was able to tell me whether
my goal of reducing process bouncing had been achieved -- for
all other things I agree that it is fairly high up on the
bogosity scale (I'd give it an 8)...
regards,
Rik -- the flu hits, the flu hits, the flu hits -- MORE
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