Re: slab redzoning

[William Lee Irwin III]

William Lee Irwin III wrote:
>> It returns a false positive when size + 3*BYTES_PER_WORD == 2**n, e.g.
>> size == 16373. Here, fls(size - 1) == 13, but fls(size - 1 + 12) == 13
>> while size - 1 + 12 == 16384, where we'd want the check to fail.

On Sat, May 22, 2004 at 10:43:47AM +0200, Manfred Spraul wrote:
> No, 16373 must fail: After adding 12 bytes the object size would be 
> 16385, which would mean an order==3 allocation.
> And 16372 must succeed: 16384 is still an order==2 allocation.
> The idea is that there shouldn't be an allocation order increase due to 
> redzoning, and afaics that doesn't happen, except between 4082 and 4095 
> bytes.

Yes. While you've corrected the one-offs in my post (arithmetic is boring,
we have machines to do that for us now), 16372 remains in question as
far as I can tell.


-- wli
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