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SubjectRe: 2.6 /proc/interrupts fails on systems with many CPUs

On Tue, 11 Nov 2003, Martin J. Bligh wrote:
> I think it'd make more sense to only use vmalloc when it's explicitly
> too big for kmalloc - or simply switch on num_online_cpus > 100 or
> whatever a sensible cutoff is (ie nobody but you would ever see this ;-))

No, please please please don't do these things.

vmalloc() is NOT SOMETHING YOU SHOULD EVER USE! It's only valid for when
you _need_ a big array, and you don't have any choice. It's slow, and it's
a very restricted resource: it's a global resource that is literally
restricted to a few tens of megabytes. It should be _very_ carefully used.

There are basically no valid new uses of it. There's a few valid legacy
users (I think the file descriptor array), and there are some drivers that
use it (which is crap, but drivers are drivers), and it's _really_ valid
only for modules. Nothing else.

Basically: if you think you need more memory than a kmalloc() can give,
you need to re-organize your data structures. To either not need a big
area, or to be able to allocate it in chunks.


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