Re: [PATCH 2/3] make new alloc_pages_exact()

From: Timur Tabi
Date: Wed Apr 27 2011 - 17:42:27 EST


Dave Hansen wrote:
>> Is there an easy way to verify that alloc_pages_exact(5MB) really does allocate
>> > only 5MB and not 8MB?

> I'm not sure why you're asking. How do we know that the _normal_
> allocator only gives us 4k when we ask for 4k? Well, that's just how it
> works. If alloc_pages_exact() returns success, you know it's got the
> amount of memory that you asked for, and only that plus a bit of masking
> for page alignment.
>
> Have you seen alloc_pages_exact() behaving in some other way?

I've never tested this part of alloc_pages_exact(), even when I wrote (the first
version of) it. I just took it on faith that it actually did what it was
supposed to do.

--
Timur Tabi
Linux kernel developer at Freescale

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