Hi Luca, Ok, that seems like a good explanation :) I will investigate if changing that value allows me to decrease poll rate and improves performances and if so I will create a PR.
thanks, F 2017-10-24 16:36 GMT+02:00 Luca Boccassi <luca.bocca...@gmail.com>: > On Tue, 2017-10-24 at 15:43 +0200, Francesco wrote: > > Hi all, > > I'm running a process that creates a ZMQ_SUB socket and is subscribed > > to > > several publishers (over TCP transport). > > > > Now I measured that this process saturates with CPU at 100% and > > slows-down > > the publisher (I'm using ZMQ_XPUB_NODROP=1) when subscribed to more > > than > > 600kPPS/1.6Gbps of traffic. > > > > The "strange" thing is that when it's subscribed to much lower > > traffic > > (e.g,. in my case to around 4 kPPS / 140 Mbps) the CPU still stays at > > 100%. > > If I strace the process I find out that: > > > > # strace -cp 48520 > > > > strace: Process 48520 attached > > ^Cstrace: Process 48520 detached > > % time seconds usecs/call calls errors syscall > > ------ ----------- ----------- --------- --------- ---------------- > > 93.29 0.634666 2 327545 poll > > 6.70 0.045613 2 23735 read > > 0.01 0.000051 4 12 write > > 0.00 0.000001 1 1 restart_syscall > > ------ ----------- ----------- --------- --------- ---------------- > > 100.00 0.680331 351293 total > > > > the 93% of the time is spent inside poll(), which happens to be > > called with > > this stack trace: > > > > #0 poll () at ../sysdeps/unix/syscall-template.S:84 > > #1 0x00007f98da959a1a in zmq::signaler_t::wait(int) () > > #2 0x00007f98da937f75 in zmq::mailbox_t::recv(zmq::command_t*, int) > > () > > #3 0x00007f98da95a3a7 in zmq::socket_base_t::process_commands(int, > > bool) > > [clone .constprop.148] () > > #4 0x00007f98da95c6ca in zmq::socket_base_t::recv(zmq::msg_t*, int) > > () > > #5 0x00007f98da97e8c0 in zmq_msg_recv () > > > > Maybe I'm missing something but by looking at the code it looks to me > > that > > this is happening because of the config setting > > 'inbound_poll_rate=100'; > > that is, every 100 packets received zmq_msg_recv() will do an extra > > poll. > > > > Now my question is: is there any reason to have this > > inbound_poll_rate setting hardcoded and not configurable (e.g., via > > context > > option) ? > > It might be as simple as nobody has needed it beforehand. I guess one > issue could be that by changing those values it's extremely easy to > shoot oneself in the foot. > But if you need it feel free to send a PR to implement the option. > > -- > Kind regards, > Luca Boccassi > _______________________________________________ > zeromq-dev mailing list > zeromq-dev@lists.zeromq.org > https://lists.zeromq.org/mailman/listinfo/zeromq-dev > >
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