Thread query SDL_Net

Question

Running my listen function in a seperate thread seems to use up a lot of CPU Is it considered ok to use Delays to reduce cpu usage or am I using threads all wrong ?

// Running in a seperate Thread
void Server::listen()
{ 
    while (m_running)
    {
        if (SDLNet_UDP_Recv(m_socket, m_packet) > 0)
        {
              //Handle Packet Function
        }
    }
}

Also, remember that [`SDLNet_UDP_Recv`](http://sdl.beuc.net/sdl.wiki/SDLNet_UDP_Recv) returns `-1` *on error*, which is non-zero and therefore true. You need to do e.g. `if (SDLNet_UDP_Recv(...) > 0)` — Some programmer dude, Feb 18 '17 at 12:43
I am 99% sure they are blocking. Also I do have > 0, I just quickly type out a minimal example. Apologies for the mistake. — user3220058, Feb 18 '17 at 12:44

score 0 · Accepted Answer · answered Feb 18 '17 at 12:49

From the SDLNet_UDP_Recv reference

This is a non-blocking call, meaning if there's no data ready to be received the function will return.

That means if there's nothing to receive then SDLNet_UDP_Recv will return immediately with 0 and your loop will iterate and call SDLNet_UDP_Recv again which returns 0 and so on. This loop will never sleep of pause, so of course it will use as much CPU as it can.

A possible solution is indeed to add some kind of delay or sleep in the loop.

I would suggest something like

while (m_running)
{
    int res;
    while (m_running && (res = SDLNet_UDP_Recv(...)) > 0)
    {
        // Handle message
    }

    if (res < 0)
    {
        // Handle error
    }
    else if (m_running /* && res == 0 */)
    {
        // Small delay or sleep
    }
}

Thanks, my main issue was if using a SDL_Delay was a valid solution. Sorry yes, non blocking also. Not with it today. — user3220058, Feb 18 '17 at 13:02

Thread query SDL_Net

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