Hi, ----- Original Message ----- > So, after finding out that nc has a stupidly small buffer size (2k > even though there is space for 16k), I was still not getting as good > as performance using nc between machines, so I decided to generate some > flame graphs to try to identify issues... (Thanks to who included a > full set of modules, including dtraceall on memstick!) > > So, the first one is: > https://www.funkthat.com/~jmg/em.stack.svg > > As I was browsing around, the em_handle_que was consuming quite a bit > of cpu usage for only doing ~50MB/sec over gige.. Running top -SH shows > me that the taskqueue for em was consuming about 50% cpu... Also pretty > high for only 50MB/sec... Looking closer, you'll see that bpf_mtap is > consuming ~3.18% (under ether_nh_input).. I know I'm not running tcpdump > or anything, but I think dhclient uses bpf to be able to inject packets > and listen in on them, so I kill off dhclient, and instantly, the taskqueue > thread for em drops down to 40% CPU... (transfer rate only marginally > improves, if it does) > > I decide to run another flame graph w/o dhclient running: > https://www.funkthat.com/~jmg/em.stack.nodhclient.svg > > and now _rxeof drops from 17.22% to 11.94%, pretty significant... > > So, if you care about performance, don't run dhclient... > Yes, I've noticed the same issue. It can absolutely kill performance in a VM guest. It is much more pronounced on only some of my systems, and I hadn't tracked it down yet. I wonder if this is fallout from the callout work, or if there was some bpf change. I've been using the kludgey workaround patch below. diff --git a/sys/net/bpf.c b/sys/net/bpf.c index cb3ed27..9751986 100644 --- a/sys/net/bpf.c +++ b/sys/net/bpf.c _at__at_ -2013,9 +2013,11 _at__at_ bpf_gettime(struct bintime *bt, int tstype, struct mbuf *m) return (BPF_TSTAMP_EXTERN); } } +#if 0 if (quality == BPF_TSTAMP_NORMAL) binuptime(bt); else +#endif getbinuptime(bt); return (quality); > -- > John-Mark Gurney Voice: +1 415 225 5579 > > "All that I will do, has been done, All that I have, has not." > _______________________________________________ > freebsd-current_at_freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org" >Received on Tue Jun 10 2014 - 01:13:38 UTC
This archive was generated by hypermail 2.4.0 : Wed May 19 2021 - 11:40:49 UTC
