2014-05-19 22:12 GMT-04:00 erik quanstrom <quans...@quanstro.net>: > i get a 126% difference executing lock xadd 1024*1024 times > with no branches using cores 4-7 of a xeon e3-1230. i'm sure it would > be quite a bit more impressive if it were a bit easier to turn the timer > interrupt off.
Dunno what to say. I'm not trying this on Plan 9, and I can't reproduce your results on an i7 or an e5-2690. I'm certainly not claiming that all pipelines, processors, and caches are equal, but I've simply never seen this behavior. I also can't think of an application in which one would want to execute a million consecutive LOCK-prefixed instructions. Perhaps I just lack imagination. --dho > i really wish i had a four package system to play with right now. that > could yield some really fun numbers. :-) > > - erik > > example run. output core/cycles. > ; 6.lxac > 4 152880511 > 7 288660939 > 6 320991900 > 5 338755451 > >
