Re: support for more than 32 CPUs

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Mon, Apr 16, 2012 at 11:05:04PM +0200, Manuel Bouyer wrote:
> Hello,
> the attached patch, based on a patch sent by Mindaugas Rasiukevicius
> on tech-kern@ some time ago, bumps the max number of CPUs to 256 for
> amd64, and should easily allow up to 64 for Xen/amd64. I tested it
> on a x86 with 64 AMD cores (lighly as this box has now known drive yet - some
> driver hacking is needed), 8 intel cores and with a Xen domU with 4 core.
> I didn't notice regressions so far.
> 
> Comments before I commit ?

Only that for even a compilation workload, we seem to lose performance
after about 15 CPUs, so though we'll probe more CPUs this way... there
may be less benefit than one would expect.

Thor