CODEWITHSUNDEEP
linuxmulticorepowerpc
Russ
Russ

Reputation: 83

How do I get the CPU ID on a multi-core PowerPC?

I have a multi-threaded app which is running under Linux 2.6.30 on an 8 core PowerPC processor. I want to determine which CPU is being used when a thread is launched. The obvious answer is to print the PID - processor ID special purpose register. The PID register is accessed using the mfspr instruction. I try to access it using the following asm in my C program:

asm(" mfspr %0, 286 " : "=r" (cpu_no));

The problem is that mfspr is a privileged instruction, and even when this app is run as root, it faults with an illegal instruction error. This instruction works fine when executed on a bare metal app.

While it is possible to create a driver which would execute this instructions in kernel-space, by the time the answer got back to the thread it might have moved to a different core.

From a Linux user level process is there any way to get the id of the core that the current thread is running on?

Upvotes: 3

Views: 2812

Answers (2)

Ejaz Ahmed
Ejaz Ahmed

Reputation: 1

Another way is to use WHOAMI register. WHOAMI register returns CPU ID of the core reading it.

Upvotes: -1

Duck
Duck

Reputation: 27572

Will pthread_getaffinity_np or sched_getcpu suffice?

Upvotes: 3

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