Re: Severe IRQ problems on Foster (P4 Xeon) system

[Alan Cox]

> If several processors are idle, say CPU0 busy and CPU[123] idle, does it
> preferentially use a "CPU" on another chip? And does that make any
> difference? It's not clear to me if the HT CPUs share cache or not, they
> obviously share bandwidth from L2 to RAM.

The scheduler changes try to schedule onto a new true CPU rather than a
sibling first. Typically you only gain 10-30% via the HT feature so you
want to load the "real" CPU's properly. 

> I'm looking at P4 chips and boards, my 2Q02 budget has some $$ for a
> system. I also will be getting some laptops 3Q02, does the new P4-M mobile
> chip by any chance have HT? If so a good reason to go Intel, assuming that
> either the BIOS or Linux can get it to use the feature ;-)

At the moment HT is Xeon only. Linux can do the right thing with it as of
2.4.18 + acpismp=force. Autodetect should be in soon. I don't know about
Intel's future product plans for HT.

Alan