From: William Lee Irwin III <wli@holomorphy.com>
To: Manfred Spraul <manfred@colorfullife.com>
Cc: mpm@selenic.com, linux-kernel@vger.kernel.org
Subject: Re: slab redzoning
Date: Sat, 22 May 2004 01:52:36 -0700 [thread overview]
Message-ID: <20040522085236.GL2161@holomorphy.com> (raw)
In-Reply-To: <40AF12C3.80902@colorfullife.com>
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
next prev parent reply other threads:[~2004-05-22 8:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-05-22 3:49 slab redzoning William Lee Irwin III
2004-05-22 8:02 ` Manfred Spraul
2004-05-22 8:26 ` William Lee Irwin III
2004-05-22 8:43 ` Manfred Spraul
2004-05-22 8:52 ` William Lee Irwin III [this message]
2004-05-22 12:22 ` Manfred Spraul
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