Is there a way to change the number of processors a program sees?

Question

Is there any way I can trick a program into thinking the system has fewer processors? To explain: I am debugging a program that creates as many threads as it has processors, using sysconf(_SC_NPROCESSORS_CONF);. I'd like to test it using only one threat. Strictly for convenience, I'd like to know if there's a way I can trick the program into thinking the computer only has one processor, to avoid having to add a command line option or changing the code to temporarily only create one thread.

Related: http://unix.stackexchange.com/questions/23106/limit-process-to-one-cpu-core — Mark Plotnick, Jan 26 '15 at 19:30
You can override any library/system call with LD_PRELOAD or ptrace. I don't know if there's a ready-made solution. — Gilles 'SO- stop being evil', Jan 26 '15 at 20:47
You could run it under a virtual machine that only has one virtual processor. — Barmar, Jan 26 '15 at 22:12

score 1 · Answer 1 · answered Jan 27 '15 at 09:18

1

Under FreeBSD (>=7.1), you can use the /usr/bin/cpuset command eg :

# cpuset -l 0,2 -c -p <pid>

Under Linux, see : http://man7.org/linux/man-pages/man7/cpuset.7.html

answered Jan 27 '15 at 09:18

Is there a way to change the number of processors a program sees?

1 Answers1