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SubjectRe: [PATCH]: Fix SMP-reordering race in mark_buffer_dirty


On Wed, 2 Apr 2008, Linus Torvalds wrote:
>
> Core 2 is the outlier in having a noticeably faster "mfence" than atomic
> instructions

Side note: mfence is probably faster than 6 cycles on Core 2. I've seen it
be basically zero-cost. Try adding a few memory ops around it - the timing
will probably change. Core 2 has this odd behaviour that it sometimes does
worse on the *really* trivial things that don't happen in real life.

Linus


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