Re: Linux 2.4.17-pre5

From: Eric W. Biederman (
Date: Tue Dec 11 2001 - 04:00:23 EST

Alan Cox <> writes:

> > If you number each CPU so its two IDs are smp_num_cpus()/2
> > apart, you will NOT need to put some crappy hack in the
> > scheduler to pack your CPUs correctly.
> Which is a major change to the x86 tree and an invasive one. Right now the
> X86 is doing a 1:1 mapping, and I can offer Marcelo no proof that somewhere
> buried in the x86 arch code there isnt something that assumes this or mixes
> a logical and physical cpu id wrongly in error.

Actually we don't do a 1:1 physical to logical mapping. I currently
have a board that has physical id's of: 0:6 and logical id's of 0:1
with no changes to the current x86 code.
> At best you are exploiting an obscure quirk of the current scheduler that is
> quite likely to break the moment someone factors power management into the
> idling equation (turning cpus off and on is more expensive so if you idle
> a cpu you want to keep it the idle one for PM). Congratulations on your
> zen like mastery of the scheduler algorithm. Now tell me it wont change in
> that property.

The idea of a cpu priority for filling sounds like a nice one. Even
if we don't use the cpu id bits for it.


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

This archive was generated by hypermail 2b29 : Sat Dec 15 2001 - 21:00:19 EST