i7 Macbook Pro CPU Usage

[Andrew07]

Running Logic Pro I'm getting strange CPU usage results in Activity Monitor.

Screenshot one is of a Logic session playing back. Activity Monitor displays CPU% at 139%. What does "Threads" designate?

Screenshot two is of a YouTube video playing via Firefox. Its CPU usage is 47%, while "Threads" jumps up to 28.

 

[drambuie]

It looks like the Logic Pro CPU% reading is an artifact of the dual cores with HT. If you look at the CPU usage graphs all 4 cores are in use, so Logic Pro it HT aware and can utilize the virtual HT cores. If you divide the 139% you get around 34%, which corresponds closely with the CPU user percentage. Your second Activity Monitor screen shows that only the two main cores are in use, and everything agrees.

Threads are different branches, or tasks, within processes that can be acted on concurrently, although not necessarily simultaneously. Simultaneous thread processing depends on the number of CPUs.

HT is sort of smoke and mirrors. A dual core CPU with HT can only process two threads at one time, as each core still has only one arithmetic unit and register set, although there are increased pipelines into the core for HT. HT aware applications think the virtual HT cores are real cores and the OS dispatches the threads accordingly. This increases the efficiency of processing threads, so that an application can complete its tasks more quickly.

 

[Andrew07]

Ah. Thank you for such a thorough reply. I assumed that "threads" within the Activity Monitor corresponded to hyper threading and that Logic was not utilizing this feature as efficiently as Firefox --thanks for clearing that up.