[zeromq-dev] zmq context's thread priority

Leonard Michelet leonard.michelet at openwide.fr
Mon Jun 8 12:30:50 CEST 2015

Hello, I use ZeroMQ on a Preempt_rt kernel and I have some connection problem on a virtual machine.
I run automated tests on this virtual machine and its CPU is quite busy, and I noticed that my real time application, which use zmq, has 2 threads not with real time scheduler, but time shared.
These thread are usually in "epoll_wait" kernel's function, and I suppose it's internal thread created by ZeroMQ (I set ZMQ_IO_THREADS to 1).
I would like to know what is the purpose of these thread, to understand what symptoms I could have if these thread were never run because of not enough CPU time.
Would it prevent me from receiving message? Would it prevent me to send message? Both?

And my next question would be : is there a way to set priority on these thread?

Thanks for reading.

P.S : the application set real time priority using pthread_setschedparam which is a per thread setting, so it doesn't change the defaullt priority of new thread, and we would like to avoid setting such a default.

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