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SubjectRe: bootmem allocator
Ingo Molnar wrote:
> * Andi Kleen <andi@firstfloor.org> wrote:
>
>>> hm, bootmem allocator is supposed to clear memory. We have a couple
>>> of places that rely on that.
>> I was actually considering to change that for the GB pages hugetlbfs
>> patchkit, because memset for 1G is a little slow and not needed (will
>> be cleared later anyways) and it might be a problem for very large
>> systems with a lot of such pages at boot.
>
> changing the default behavior of bootmem alloc to be non-clearing is a
> really bad idea that will only cause unrobustness. The proper approach
> is to add an _opt-in_ API that does not clear memory
> (bootmem_alloc_dontclear() or whatever), available to callers that know
> it for sure that they dont need the clearing.

Yes, changing the default of bootmem_alloc is a bad idea. I just changed
a bunch of static arrays to bootmem alloc's and it was pointed out early
that not only does bootmem_alloc clear memory, but also panics if it's not
available.

> Also take into account that alloc_bootmem_low() :
> - calls panic() if not enough memory
> - already clears allocated memory
> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>

A specialized call to bootmem_alloc probably needs it's own API... ;-)

Thanks,
Mike


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