Messages in this thread | | | Date | Wed, 24 Aug 2011 08:53:44 -0500 (CDT) | From | Christoph Lameter <> | Subject | Re: [PATCH 13/15] x86: add cmpxchg_flag() variant |
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On Tue, 23 Aug 2011, Jeremy Fitzhardinge wrote:
> However, having prototyped it, I dunno, it doesn't really seem like much > of a win for all the extra code it adds. I just can't get too excited > about an extra test instruction adjacent to a monster like a locked > cmpxchg. The jump variant avoids the test, but gcc still generates some > pretty bogus stuff:
There are also unlocked cmpxchges in use. And if the cmpxchg is a 16 byte cmpxchg (cmpxchg_double) then the comparison is getting more expensive.
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