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How can the CPU affinity of a process be set in kernel module? In user mode there is a syscall sched_setaffinity, but I am looking for the kernel mode equivalent.
In the Linux kernel code, there is also a function called sched_setaffinity. It's called from the sys_sched_setaffinity function which is called by system_call. From what it seems, this is the function that I want to use. The fact that it has the same name as the system call makes me a bit uneasy, though.
But as we all know, the best thing to do is to just try it. So I did, and my module compiled. However, when I try to load the module, it complains that the name sched_setaffinity is undefined.
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To set the CPU affinity of a process, you can use taskset program and sched_setaffinity system call. To set the CPU affinity of a thread, you can use pthread_setaffinity_np and pthread_attr_setaffinity_np.
As per Wikipedia, Processor affinity, or CPU pinning or “cache affinity”, enables the binding and unbinding of a process or a thread to a central processing unit (CPU) or a range of CPUs, so that the process or thread will execute only on the designated CPU or CPUs rather than any CPU.
Method 1: System-wide System-wide we can set the boot. ini setting to use /numproc=4 so that the machine only uses 4 cores irrespective of the number of cores available (provided that there are 4 or more cores available) Method 2: Task Manager First, select a process from Task Manager. Then, click “Set affinity”.
sched_setaffinity is not exported to modules.
If you modify /usr/src/linux/kernel/sched.c, you can cause sched_setaffinity to be exported to modules.
long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
{
...
}
+EXPORT_SYMBOL_GPL(sched_setaffinity);
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