On Tue, 2017-10-31 at 10:42 +0100, Francesco wrote: > Hi, > just to update on this topic, in case it's useful to others: it > turned out > that the bottleneck was only in minor part related to the setting of > the inbound_poll_rate > itself: the problem was more on the fact that I was calling > zmq_poll() > before each zmq_msg_recv() (to implement a timeout on the recv()). > The way I fixed the problem was to implement a slightly smarter > polling > logic: I try to receive with ZMQ_DONTWAIT flag. Then if 0 messages > are > received, next time a poll() operation with my desidered timeout will > be > performed before attempting the recv(). If 1 message is received > instead > then the next time the same recv() (always with ZMQ_DONTWAIT flag) > will be > repeated. > > In this way I found that I could reduce greatly the number of poll > operations (and thus increase the performances when a lot of messages > are > incoming) but also keep my desired behaviour of a timeout-enabled > recv(). > > HTH, > Francesco
If all you are looking for a recv with a timeout, there's a socket option for that, ZMQ_RCVTIMEO > 2017-10-24 19:48 GMT+02:00 Francesco <francesco.monto...@gmail.com>: > > > 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 > > > > <045%20613> 2 23735 read > > > > 0.01 0.000051 4 12 write > > > > > > > > 0.00 0.000001 1 1 restart_syscal > > > > l > > > > ------ ----------- ----------- --------- --------- ------------ > > > > ---- > > > > 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 > > > > > > > > _______________________________________________ > zeromq-dev mailing list > zeromq-dev@lists.zeromq.org > https://lists.zeromq.org/mailman/listinfo/zeromq-dev -- Kind regards, Luca Boccassi
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