I am currently working on a project about setting process to one core in linux environment. I use sched_setaffinity to do this job and I wonder whether there are some functions provided by linux to get which core the process is running on. I use top command and find it could get this info using j option. So i am sure there are some ways to get this info in user space.
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You probably want sched_getcpu(). If you are running an older version of glibc, you can read the 39th field of /proc/[pid]/stat for the appropriate pid -- see the proc(5) man page for more details.
llasram
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Unfortunately, my Glibc version is under 2.6 so it could not work – terry Sep 12 '10 at 03:56
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Ok. Modified my answer to include a solution for pre-2.6 glibcs. – llasram Sep 12 '10 at 09:36
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You can use inline assembly (on a x86 arch) to achieve this:
mov eax, 1 ; cpuid functionality depends on the value of eax
cpuid ; get cpu info
shr ebx, 24 ; ebx[31:24] is the cpu ID.
mov eax, ebx ; eax contains the cpu ID
you can read more about CPUID instruction here http://download.intel.com/design/processor/applnots/24161832.pdf
AmirW
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Thanks for your suggestions, however my cpu is xeon 5560 and the os is RHEL 5.4 64bit. Could CPUID still work as registers all changed names? – terry Sep 12 '10 at 03:59