Messages in this thread | | | Date | Wed, 26 Jul 2006 09:25:08 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: Re: [patch] slab: always follow arch requested alignments |
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On Wed, 26 Jul 2006, Pekka Enberg wrote:
> On 7/26/06, Christoph Lameter <clameter@sgi.com> wrote: > > We intentionally discard the caller mandated alignment for debugging > > purposes. > > Disagreed. The caller mandated alignment is not a hint. It is the > required minimum alignment for objects.
This has been with the slab for a long time. Lots of alignments are now ignored for the debugging case without a problem. Manfred intentionally put that in. Alignments passed to kmem_cache_create are there for performance reasons and not because unaligned object break the arch code.
> On 7/26/06, Christoph Lameter <clameter@sgi.com> wrote: > > And it changes the basic way that slab debugging works. > > Look at kmem_cache_create, we turn off debugging for both caller and > architecture mandated alignments already and the only reason we are > not doing it for Heiko is because the architecture recommended default > alignment is so large.
We discard alignment for FORCED_DEBUG unless
1. object size > 4096
2. If the object size would increase unreasonably.
I simply added another case. That preseves the discarding of alignment for the FORCED_DEBUG case but allows an override if operations would be impossible for not correctly aligned objects for certain caches (like in the S/390 case). - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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