Re: #tj-percpu has been rebased

From: H. Peter Anvin
Date: Wed Feb 18 2009 - 01:44:24 EST


Rusty Russell wrote:
>>>
>> num_possible_cpus() can be very large though, so in many cases the
>> likelihood of finding that many pages approach zero. Furthermore,
>> num_possible_cpus() may be quite a bit larger than the actual number of
>> CPUs in the system.
>
> Sure, so we end up at vmalloc. No worse, but simpler and much better if we
> *can* do it.
>

If the likelihood is near zero, then you're wasting opportunities to do
it better. If we have compact per-cpu virtual areas then we can use
large pages if we know we'll have large percpu areas.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.

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