Re: [PATCH] hwpmc(4) changes to use 'mp_maxid' instead of 'mp_ncpus'.

On Mon, Mar 17, 2008 at 09:47:25AM -0400, John Baldwin wrote:
On Saturday 15 March 2008 01:43:00 am Joseph Koshy wrote:
FreeBSD has been trying to not be quite as i386-centric as it used to
be. If you look at other code in the kernel that handles per-cpu data
such as UMA you will see that it uses mp_maxid and CPU_ABSENT(). There
are other places in the kernel that are broken though (such as ndis(4)).

HWPMC is very x86 centric, for obvious reasons.

Considering other CPU archictectures support various performance counters it
really shouldn't be designed to be x86-centric even if it is currently only
implemented for x86 CPUs.

We should take some care to make sure we don't over generalize. From
what I've heard the people who wrote the performance counter framework
for x86 in linux where very, very unhappy when told to rework everything
to support at framework that went with ia64's exponentionaly more
complex instrumentation. If we can make small changes to support more
conventional non-x86 platforms, that's probably a good idea. If nothing
else, these counters could be even more useful on CPU-poor embedded
devices.

-- Brooks

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