Re: [PATCH] MM: implement MADV_FREE lazy freeing of anonymous memory

Nick Piggin
2007-05-08T23:24:19Z

Rik van Riel wrote:
> Nick Piggin wrote:
>
>> We have percpu and cache affine page allocators, so when
>> userspace just frees a page, it is likely to be cache hot, so
>> we want to free it up so it can be reused by this CPU ASAP.
>> Likewise, when we newly allocate a page, we want it to be one
>> that is cache hot on this CPU.
>
>
> Actually, isn't the clear page function capable of doing
> some magic, when it writes all zeroes into the page, that
> causes the zeroes to just live in CPU cache without the old
> data ever being loaded from RAM?
>
> That would sure be faster than touching RAM. Not sure if
> we use/trigger that kind of magic, though :)
>

powerpc has and uses an instruction to zero a full cacheline, yes.

Not sure about x86-64 CPUs... I don't think they can do it.

--
SUSE Labs, Novell Inc.