> -----Original Message----- > From: Martin Sebor [mailto:[EMAIL PROTECTED] On Behalf Of Martin Sebor > Sent: Thursday, July 26, 2007 7:50 PM > To: stdcxx-dev@incubator.apache.org > Subject: Re: atomic tests timing out on Windows
> As I understand the technology, the benefit of hyperthreading > is in the processor's ability to make use of its idle > circuits while other circuits are busy doing things. But > because a HT processor does not actually duplicate most of > ordinary processor's circuits (I've seen 5% being tossed > around as the increase in the number of transistors between > an ordinary CPU and one with HT) it means that while one > thread that does FP processing can execute in parallel with > another that does integer arithmetic, two threads that are > doing the same thing cannot actually run simultaneously. > > In our case, since both threads do exactly the same thing, > trying to run them on their own virtual "processors" > (emulated by HT) must make them run essentially serially just > as they would on an ordinary uniprocessor, and the scheduling > overhead involved in the OS and CPU switching between the two > threads must actually account for most of time spent by the process. > > If my analysis is correct, we should avoid scheduling the > threads on multiple logical CPUs on HT systems with a single > physical CPU. > Do you agree? I agree. Now we need to know how to determine if the CPU has more than 1 logical CPU. And I think it is possible to make machine with 2 HT-supporting CPU on board? Here (http://www.intel.com/cd/ids/developer/asmo-na/eng/275339.htm) I found the program with sources, that will help us. Farid.
