Re: [patch 2/2] slab: always consider arch mandated alignment

From: Christoph Lameter
Date: Wed Jul 26 2006 - 14:58:10 EST

On Wed, 26 Jul 2006, Manfred Spraul wrote:

> > Thus the patch is correct, it's a bug in the slab allocator. If
> > > is set, then the allocator ignores align or ARCH_SLAB_MINALIGN.
> >
> >
> > But then Heiko does not want to set ARCH_SLAB_MINALIGN at all. This is not
> > the issue we are discussing. In the DEBUG case he wants
> > ARCH_KMALLOC_MINALIGN to be enforced even if ARCH_SLAB_MINALIGN is not set.
> >
> The kmalloc caches are allocated with HWCACHE_ALIGN+ARCH_KMALLOC_MINALIGN. The
> logic in kmem_cache_create didn't handle that case correctly.
> On most architectures, ARCH_KMALLOC_MINALIGN is 0. Thus SLAB_DEBUG redzones
> everything.
> On s390, ARCH_KMALLOC_MINALIGN is 8. This disables redzoning.
> Ok?

So Redzoning etc will now be diabled regardless even if
ARCH_SLAB_MINALIGN is not set but another alignment is given to

So we sacrifice the ability to worsen the performance of slabs by
misaligning them for debugging purposes.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at