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Copy pathcpu_affinity.cpp
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47 lines (40 loc) · 1.98 KB
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#include <thread>
#include <iostream>
#include <pthread>
// Note how we use the native_handle method discussed earlier in order to pass the underlying native handle to the pthread call (it takes a pthread_t ID as its first argument). The output of this program on my machine is:
// On Linux, we can use the pthread-specific pthread_setaffinity_np function. Here's an example that reproduces what we did before, but this time from inside the program. In fact, let's go a bit more fancy and pin each thread to a single known CPU by setting its affinity:
int main(int argc, const char** argv) {
constexpr unsigned num_threads = 4;
// A mutex ensures orderly access to std::cout from multiple threads.
std::mutex iomutex;
std::vector<std::thread> threads(num_threads);
for (unsigned i = 0; i < num_threads; ++i) {
threads[i] = std::thread([&iomutex, i] {
std::this_thread::sleep_for(std::chrono::milliseconds(20));
while (1) {
{
// Use a lexical scope and lock_guard to safely lock the mutex only
// for the duration of std::cout usage.
std::lock_guard<std::mutex> iolock(iomutex);
std::cout << "Thread #" << i << ": on CPU " << sched_getcpu() << "\n";
}
// Simulate important work done by the tread by sleeping for a bit...
std::this_thread::sleep_for(std::chrono::milliseconds(900));
}
});
// Create a cpu_set_t object representing a set of CPUs. Clear it and mark
// only CPU i as set.
cpu_set_t cpuset;
CPU_ZERO(&cpuset);
CPU_SET(i, &cpuset);
int rc = pthread_setaffinity_np(threads[i].native_handle(),
sizeof(cpu_set_t), &cpuset);
if (rc != 0) {
std::cerr << "Error calling pthread_setaffinity_np: " << rc << "\n";
}
}
for (auto& t : threads) {
t.join();
}
return 0;
}