[zeromq-dev] adding timeout in zmq_poll

Martin Sustrik sustrik at 250bpm.com
Mon Dec 28 14:17:05 CET 2009


Pavel Gushcha wrote:

>         2) If user specified too small timeout (1 nsec) must we increase
>         this timeout to one ms in linux and 1microsec in windows?
> 
> 
>     I would rather decrease the number. The semantics of the timeout is
>     "zmq_poll will return before the timeout expires" (see the previous
>     discussion on returning with no events).
> 
> 
> If specified timeout is greater than OS API timeout granularity we can 
> without problem decrease it. I speak about case, when user specified 
> timeout lesser, than timeout granularity in OS API. Timeout will be 
> calculated as zero and user will get 100% cpu usage in thread that 
> executes zmq_poll() in loop.

I don't think that's a problem. If you specify very low timeout, high 
CPU usage is to be expected. It's a natural behaviour.

On the other hand, not adhering to timing guarantees can cause serious 
problems in real-time applications.

Martin



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