Messages in this thread | | | Date | Wed, 26 Jul 2006 20:24:18 +0200 | From | Manfred Spraul <> | Subject | Re: [patch] slab: always follow arch requested alignments |
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Pekka Enberg wrote:
> Hi Christoph, > > On 7/26/06, Christoph Lameter <clameter@sgi.com> wrote: > >> We intentionally discard the caller mandated alignment for debugging >> purposes. > > There are two different types of alignment: - SLAB_HWCACHE_ALIGN: it's a recommendation, it's regularly ignored. - the align parameter, or ARCH_SLAB_MINALIGN: It's mandatory. For example the pgd structures must be 4 kB aligned, it's required by the hardware. And I think there was (is?) a structure where ptr & ~(size-1) was used to find the start of the structure.
Thus the patch is correct, it's a bug in the slab allocator. If HWCACHE_ALIGN is set, then the allocator ignores align or ARCH_SLAB_MINALIGN.
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