source: doc/theses/thierry_delisle_PhD/code/readyQ_proto/ntmove.cpp @ d66a43b

#include <atomic>
#include <iostream>
#include <locale>
#include <thread>

#include <x86intrin.h>

struct __attribute__((aligned(128))) Global_t {
        volatile size_t value;
} global;

static const size_t iterations = 1'000'000'000;

size_t read() {
        // size_t r = __atomic_load_n(&global.value, __ATOMIC_RELAXED);
        // _mm_stream_si64((long long int*)&global.value, r);
        // // _mm_clflush( (void*)&global.value );
        // // __builtin_prefetch((void*)&global.value);
        // asm volatile(
        //      "PREFETCHNTA %[target]"
        //      :
        //      : [target] "m" (global.value)
        // );
        // return r;
        return __atomic_load_n(&global.value, __ATOMIC_SEQ_CST);

        // __m128i r = _mm_stream_load_si128((__m128i*)&global.value);
        // asm volatile(
        //      "PREFETCHNTA %[target]"
        //      :
        //      : [target] "m" (global.value)
        // );
        // return ((Global_t*)&r)->value;
        // size_t r;
        // asm volatile(
        //      "MOVNTI %[target], %[r]\n\t"
        //      : [r] "=r" (r)
        //      : [target] "m" (global.value)
        // );
        // return r;
}

void write(size_t v) {
        // __atomic_store_n(&global.value, v, __ATOMIC_SEQ_CST);
        // __atomic_store_n(&global.value, v, __ATOMIC_RELAXED);
        // asm volatile(
        //      "MOVNTI %[v], %[target]\n\t"
        //      :
        //      : [target] "m" (global.value), [v] "r" (v)
        // );
        _mm_stream_si64((long long int*)&global.value, v);
}

void reader(size_t * reads, size_t * diffs, size_t * m) {
        size_t last = read();
        for(size_t i = 0; i < iterations; i++) {
                size_t val = read();
                if(last != val) (*diffs)++;
                last = val;
                if(last > *m) *m = last;
                (*reads)++;
        }
}

std::atomic<bool> done = { false };

void writer() {
        size_t v = 0;
        while(!done) {
                v++;
                write(v);
                __atomic_thread_fence(__ATOMIC_SEQ_CST);
        }
}

int main() {
        std::cout.imbue(std::locale(""));
        size_t reads = 0;
        size_t diffs = 0;
        size_t max   = 0;
        auto w = std::thread(writer);
        auto r = std::thread(reader, &reads, &diffs, &max);
        r.join();
        done = true;
        w.join();
        std::cout << reads << " " << diffs << " " << max << std::endl;
}