Hi,

The recent patches that changed the default alignment for slab caches 
affected the alignment of the kmalloc caches:
Initially the default was word alignment and it was increased for the 
kmalloc caches by setting SLAB_HWCACHE_ALIGN.
The "align" patch changed the default to cache line alignment and 
removed the SLAB_HWCACHE_ALIGN flag from the kmem_cache_create calls for 
kmalloc.
But when the default was changed back to word alignment the flag was not 
reintroduced for kmalloc.

I think the kmalloc caches should remain cache line aligned: the object 
sizes are powers of two, so there is virtually no wasted memory. What 
about the attached patch? I've added an arch override, perhaps someone 
wants unaligned kmalloc caches (caused by word offsets for coloring 
instead of cache line offsets).

An arch override is definitively needed: One of SGI's drivers needs 
cache line alignment due to hardware constraints.
--
    Manfred