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SubjectRe: [RFC][PATCH 2/3] mm: slab: move around slab ->freelist for cmpxchg
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.


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