Re: maximum number of CPUs

[Sad Clouds <cryintothebluesky%googlemail.com@localhost>]

On Thu, 23 Feb 2012 20:58:45 +0000
Mindaugas Rasiukevicius <rmind%netbsd.org@localhost> wrote:

> Brook Milligan <brook%nmsu.edu@localhost> wrote:
> > I understand that at least on the i386/amd64 ports CPUs are tracked
> > with a 32-bit mask and thus at most 32 CPUs may be active.  How
> > complex is the task of removing this limitation so that a larger
> > number of CPUs may be used?
> 
> I have a preliminary patch to support up to 255 CPUs on amd64 (not
> worth on i386), however there is still some bug in the early
> initialisation code, when TLBs are not being flushed.  I have not had
> time yet to debug it out.
> 
> http://www.netbsd.org/~rmind/x86_256_cpus_v4.diff
> 
> Apart from that bug, it should be mostly complete.
> 
> -- 
> Mindaugas

Why limit this to 255? There are systems out there that surpass this
number. I developed some code that uses a 64 element array of 64-bit
integers to give 64 * 64 = 4096 bits, which can be used to tracking
boolean on/off states.

If people are interested in using this for tracking CPU states, I can
provide the source code under BSD license.