Large machine test ideas

[Attilio Rao]

2011/9/1 Ivan Voras <ivoras at freebsd.org>:
> 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?
>

Well, there are quite a few statically allocated, but as I said,
making the kernel MAXCPU-agnostic (or sort of agnostic) is a goal and
a good project.

Thanks,
Attilio


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