On 9 maj 2012, at 20:14, [email protected] wrote:
> on 2012-05-09 9:02 Dinse, Gregg (NIH/NIEHS) [E] wrote > >> Did you get the impression that Lion decides when to activate the extra > (logical) cores, as opposed to the user having to decide (and possibly make a > choice in some preference panel)? > > it is automatic, not user-driven, but i don't know the mechanism; it's > possible that energy saver settings would have an effect > >> >> Although I always see 16 bars (in iStat Menus or MenuMeters), usually only >> every other bar moves above zero. So, my guess is that typically only the 8 >> (physical) cores are being used, but the other 8 (logical) cores can be >> activated (automatically) if a task can benefit from parallelism. > > i use iStat Menus, and on my quad-i7 laptop, i often see some activity in the > four secondary "cores", but they don't seem to "max out" like the four > primary cores do on some tasks If hyper threading is implemented and is on, the logical cores should be seen regardless of the amount of work. Your virtual cores svould have that behaviour that they aren't maxed out as often as the phisical cores. If they were, hyper threading would be a miracle, making one core become two cores in every sense. Hyper threading can in some cicumstances increase performance close to twice physiclal, but it can also degrade performance. It depends on the work at hand. HT makes sense when looked at work on avarage and for some special cases HT is better to turn of. Those who are using virtual machine software have to bear in mind the difference between physical and logical cores. Physical cores is fundament_______________________________________________ MacOSX-talk mailing list [email protected] http://www.omnigroup.com/mailman/listinfo/macosx-talk
