Re: [RFC][PATCH 2/3] mm: slab: move around slab ->freelist forcmpxchg

[Christoph Lameter]

On Wed, 11 Dec 2013, Dave Hansen wrote:

>
> The write-argument to cmpxchg_double() must be 16-byte aligned.
> We used to align 'struct page' itself in order to guarantee this,
> but that wastes 8-bytes per page.  Instead, we take 8-bytes
> internal to the page before page->counters and move freelist
> between there and the existing 8-bytes after counters.  That way,
> no matter how 'stuct page' itself is aligned, we can ensure that
> we have a 16-byte area with which to to this cmpxchg.

Well this adds additional branching to the fast paths.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/