How reliable is SLAB_HWCACHE_ALIGN?

[Ravikiran G Thirumalai]

I was assuming that if you create a slab cache with SLAB_HWCACHE_ALIGN,
objects are guaranteed to be aligned to L1 cacheline.  But this piece
of code in kmem_cache_create has raised doubts.

----------------------------------------------------------------------------
        if (flags & SLAB_HWCACHE_ALIGN) {
                /* Need to adjust size so that objs are cache aligned. */
                /* Small obj size, can get at least two per cache line. */
                while (size < align/2)
                        align /= 2;
                size = (size+align-1)&(~(align-1));
        }
----------------------------------------------------------------------------

Am I missing something or can there really be two objects on the same 
cacheline even when SLAB_HWCACHE_ALIGN is specified?

Thanks,
Kiran
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