CPU usage in pop block

[hdhog]

Used ~30% CPU on wait in pop. Compiled in VS2017

sample code:

auto q = std::make_shared<rigtorp::MPMCQueue<int>>(10);
while(true) {
    int v;
    q->pop(v);
    switch(v) {
    case 4726:
        LOGV << "event=" << v << " user removed";
        break;
    case 4724:
        LOGV << "event=" << v << " user password manually reseted";
        break;
    default:
        LOGV << "event=" << v << " unknow";
        break;
    }
}

[hdhog]

full example

CMakeLists.txt:

cmake_minimum_required(VERSION 3.14)

project(testQ)

file(GLOB SOURCES
    "*.h"
    "*.cpp"
)

add_executable(q_test ${SOURCES})

main.cpp:

#include <iostream>
#include <memory>
#include "MPMCQueue.h"

int main (int argc, char *argv[]) {
    auto q = std::make_shared<rigtorp::MPMCQueue<int>>(10);
    while(true) {
        int v;
        q->pop(v);
        switch(v) {
            case 4726:
                std::cout << "event=" << v << " user removed\n";
                break;
            case 4724:
                std::cout << "event=" << v << " user password manually reseted\n";
                break;
            default:
                std::cout << "event=" << v << " unknow\n";
                break;
        }
    }
    return 0;
}

[rigtorp]

That's expected. This queue doesn't use futex for waiting. It's intended for high performance applications. If you want to be energy efficient you can use a std::mutex + std::condition_variable with a std::deque instead.