[olug] questions about socket programming

[Eric W. Biederman]

Lou Duchez <lou at paprikash.com> writes:

> I believe you're right about socket_accept.  What I'm doing is I'm
> first checking whether there are any incoming connections via
> socket_select, which has a timeout interval that I set to 10
> microseconds -- that's enough time to tell me if there are any waiting
> connections, without idling for an extended period.  If there is a
> waiting connection,  that's when I invoke socket_accept, so the
> blocking behavior of socket_accept isn't a problem.
>
> The grand loop ("while (true) { ... }") that contains all the
> connection handling, has three parts: accepting new connections,
> reading data from existing connections, and sending data as
> appropriate to existing connections.  The "sleep" part that I feel is
> a good idea is at the end of the grand loop.

>>>> On Sat, Aug 1, 2020 at 8:26 PM Lou Duchez <lou at paprikash.com> wrote:
>>>>> 2) The code examples I've seen do not put any sort of sleep(), usleep(),
>>>>> or time_nanosleep() in the grand loop. That seems ill-advised to me;
>>>>> based on my testing, the grand loop consumes a ton of CPU unless I put a
>>>>> brief sleep (maybe one-tenth second) in each iteration.  Am I wrong to
>>>>> put the sleep in there?  Am I handling it wrong?


Are you handling it wrong?  I believe so.

You should use your socket_select or possibly even your socket_accept to
sleep.  If something comes in while they are waiting the sleep will be
cut short, so responsiveness will be maintained.   If they are allowed
to sleep long enough you will consume essentially no cpu when idle.

Eric