Re: [Lse-tech] CPUSET Proposal

David Mosberger
2003-09-25T06:57:10Z

>>>>> On Wed, 24 Sep 2003 23:02:34 -0700, William Lee Irwin III <wli@holomorphy.com> said:

Bill> On Wed, 24 Sep 2003 09:30:44 -0700, Stephen Hemminger
Bill> <shemminger@osdl.org> said:

Stephen> Looks good, but you aren't likely to get much acceptance or
Stephen> testing if it only works on ia64. You need to make a
Stephen> version for i386 as well.

Bill> On Wed, Sep 24, 2003 at 10:02:35AM -0700, David Mosberger wrote:

>> Is this true for >8-way machines?

Bill> x86's architectural limitations are 64x for serial APIC -based machines
Bill> (e.g. NUMA-Q) and 255x for xAPIC -based machines (no known extant > 32x
Bill> machines, apparently some kind of non-architectural regression), where
Bill> the non-power-of-two number of cpus is due to the broadcast ID reserved
Bill> from an 8-bit interrupt controller ID space. A likely explanation for
Bill> the current xAPIC limitations is the recommended (publicly documented)
Bill> physical APIC ID enumeration scheme breaking down for > 32x.

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

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

--david