Hi, This is a general question w.r.t multicore processor architecture. Do multicore processors share the processing efforts among all the cores equally even for a tiny work, Or, Will they share the processing efforts with other cores only if the core 1 or core 2 cross a threshold level. Any ideas ?
Thx in advans, Karthik Balaguur
This is a general question about SMP OS architecture.
There is no threshold. A core can be either busy or free. There is a common list of active threads scheduled to the execution. If any of the cores gets free, it executes the next thread from the list.
More interesting questions are how the interrupts are handled, and how the scheduler is processed. On all systems that I have seen, the interrupts and the scheduler were either dedicated to Core "A", or there was some sort of the fixed assignment between the cores. I don't know if anyone changes the interrupts and the scheduler assignment between the cores dynamically.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
A multi-core processor behaves like multiple separate processors. Each core runs what the OS decides the core should run. Cores do not (and cannot) offload processing to each other of their own accord.
If you have a single active process, and that process has a single active thread, one of the cores will be running flat-out while the other cores remain idle. If you want to utilise multiple cores, you have to have multiple active threads or processes.
The MIT RAW processor had register-mapped channels between cores, which allowed the compiler to map an expression across several dedicated cores. In effect, several cores could be combined into a VLIW.
Several other research processors (iWarp) have this kind of low-cost interconnect. It isn't common.
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