Your main loop would cause 100% loading, depending how=20
"poll_my_sockets()" worked...

If you write it like this

int main() { while(1) { let_me_know_if_my_sockets_need_attention();=20
do_work(); } }

then your program is spending most of it's time waiting for something=20
to happen.

"select" is your friend :)


On 2012-10-10 09:19, V G wrote:
> Hi all, I have a question about CPU load, task scheduling, and how a=20
> real
> operating system (like Linux/BSD/QNX) manage threads.
>
> Q: If you write a simple, single-threaded program in C as follows
>
> int main() { while(1); }
>
> and run it on a single core CPU, the CPU load shoots up to 1.00 and=20
> stays
> there. Makes sense, as all of the CPU time is spent in this thread.=20
> (All as
> in almost all, since the operating system's task scheduler and other
> processes have to run as well.)
>
> However, many single threaded network event loop libraries, as well=20
> as GUI
> libraries come with their own main loop/event loop. Your program will=20
> never
> exit from the main loop unless you kill it, but while the program is
> running, the CPU does NOT appear to be under load. What's going on=20
> here?
> How is it that the main loop is running and is responsive, yet the=20
> CPU is
> under minimal load?
>
> Even if you did something like this,
>
> int main() { while(1) { poll_my_sockets(); do_work(); } }
>
> wouldn't it use 100% of the CPU's time in the main loop? But it=20
> appears
> that all asynchronous network libraries somehow don't load up the=20
> CPU. Yes,
> CPU load is the indicator of actual CPU load, and doesn't factor in
> anything that's waiting on I/O, but shouldn't just the act of calling=20
> the
> poll function in an infinite loop still fully load the CPU?

--=20
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