Re:Intel i7 loop performance anomaly
by pron on Tuesday December 03, 2013 @05:13PM
(#6843566)
> In short, OOO cores are weird and horribly complicated and completely untrustworthy where performance is concerned.
Yep. There's a great talk about this by Cliff Click, called A Crash Course in Modern Hardware[1] that I would recommend to everyone. I am no hardware expert, so that talk really enlightened me.
Regarding the issue at hand, I remember Doug Lea saying[2] that some new Intel processors may recognize a loop as the OSs idle loop and power down the core. That's why he computes random numbers in busy-wait loops.
Yep. There's a great talk about this by Cliff Click, called A Crash Course in Modern Hardware[1] that I would recommend to everyone. I am no hardware expert, so that talk really enlightened me.
Regarding the issue at hand, I remember Doug Lea saying[2] that some new Intel processors may recognize a loop as the OSs idle loop and power down the core. That's why he computes random numbers in busy-wait loops.
[1] http://www.infoq.com/presentations/click-crash-course-modern...
[2] http://emergingtech.chariotsolutions.com/2013/04/phillyete-s...