Large machine test ideas

[Ivan Voras]

On 1 September 2011 16:11, Attilio Rao <attilio at freebsd.org> wrote:

>> I mean, if we have 2 cpus in a machine, but MAXCPU is set to 256, there
>> is a bunch of "lost" memory and higher levels of lock contention?
>>
>> I thought that attilio was taking a stab at enhancing this, but at the
>> current time anything more than a value of 64 for MAXCPU is kind of a
>> "caveat emptor" area of FreeBSD.
>
> With newest current you can redefine MAXCPU in your kernel config, so
> you don't need to bump the default value.
> I think 64 as default value is good enough.
>
> Removing MAXCPU dependency from the KBI is an important project
> someone should adopt and bring to conclusion.

That's certainly one half of it and thanks for the work, but the real
question in this thread is what Sean asked: what are the negative
side-effects of simply bumping MAXCPU to 256 by default? AFAIK, there
are not that many structures which are statically sized by MAXCMPU and
most use the runtime-detected smp_cpus?