Re: [Lse-tech] CPUSET Proposal

David Mosberger
2003-09-25T07:07:03Z

>>>>> On Wed, 24 Sep 2003 23:57:10 -0700, David Mosberger <davidm@linux.hpl.hp.com> said:
Bill> x86's architectural limitations are 64x for serial APIC -based
Bill> machines (e.g. NUMA-Q) and 255x for xAPIC -based machines (no
Bill> known extant > 32x machines, apparently some kind of
Bill> non-architectural regression), where the non-power-of-two
Bill> number of cpus is due to the broadcast ID reserved from an
Bill> 8-bit interrupt controller ID space. A likely explanation for
Bill> the current xAPIC limitations is the recommended (publicly
Bill> documented) physical APIC ID enumeration scheme breaking down
Bill> for > 32x.

Bill> Custom interrupt controllers may exceed these limits, but I
Bill> don't know of any that have actually been made use of to do
Bill> so. Though it sucks and very, very badly, x86 is not limited
Bill> to anything like 8x.

David> I wasn't suggesting that x86 is limited to 8-way, I was
David> wondering how many > 8-way x86 Linux machines are actually
David> out there. I wasn't even being facetious---just curious.

Incidentally, the first "big" SMP machine I had access to was some
sort of Sequent (S81/10?), with ~12 80386 CPUs (yes, that was a long
time ago... ;-).

--david