Cache coherency primer (2014)

Seemingly innocent code like this will most likely cause completely unnecessary inter-core traffic (assuming that the compiler has laid out a and b adjacently, and they both fall within the boundaries of a single cache line):

    unsigned a, b;

    void thread_a(void) {
        for (;;) a++;
    }

    void thread_b(void) {
        for (;;) b++;
    }