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

[Linus Torvalds]

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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