Hi, Ben, I have one follow-up question. I setup a topology with 12 hosts and 12 switches in Mininet. The hosts (acting as the packets generator to the network) should send packets around 30 pps in order to make the switches not drop packets. However, I find that the CPU/MEM usage of ovs-vswitchd is not high (both < 10%). According to your experience, where do you think is the bottleneck? How can I improve the performance of packet processing speed in userspace in Mininet?
Thanks, Xuemei On Fri, Jul 24, 2015 at 9:30 AM, Xuemei Liu <lxuemei3...@gmail.com> wrote: > Thanks very much Ben. > > On Fri, Jul 24, 2015 at 9:25 AM, Ben Pfaff <b...@nicira.com> wrote: > >> Any SLOW_* constant indicates why a packet can't be processed in the >> fast path (e.g. in the kernel). Such packets always have to be handled >> in userspace. Thus, tagging all flow translations with any SLOW_* >> constant causes them all to be sent to userspace. >> >> On Thu, Jul 23, 2015 at 05:07:58PM -0700, Xuemei Liu wrote: >> > Hi, Ben, >> > >> > After I decreased the sending rate at h1, I find s1 userspace/h2 can >> > receive all packets. What does SLOW_ACTION mean? Why this will make the >> > packets forwarded from kernel space to user space? >> > >> > Thanks, >> > Xuemei >> > >> > On Thu, Jul 23, 2015 at 4:46 PM, Ben Pfaff <b...@nicira.com> wrote: >> > >> > > Well, yes, there are performance problems, as I predicted. >> > > >> > > On Thu, Jul 23, 2015 at 04:42:17PM -0700, Xuemei Liu wrote: >> > > > Let me try to describe it. Suppose the topology is h1-s1-h2, where >> h1, h2 >> > > > are hosts, and s1 is the ovs switch. I add policy in s1 to forward >> > > packets >> > > > with dstip of h2 to h2. Then I test in two scenarios. >> > > > 1. h1 sends 9 packets (3 packet for each of 3 different flows) to >> h2. >> > > With >> > > > your methods, userspace in s1 can accept all the packets, and h2 can >> > > > receive all the 9 packets. Work perfect. >> > > > 2. h1 sends 10000 packets to h2. In this case, h2 receives the same >> > > packets >> > > > as userspace in s1 does. However, the number of packets received is >> much >> > > > less than 10000. Which means many packets are lost in s1. >> > > > Is this clear now? >> > > > >> > > > Thanks, >> > > > Xuemei >> > > > >> > > > On Thu, Jul 23, 2015 at 4:18 PM, Ben Pfaff <b...@nicira.com> wrote: >> > > > >> > > > > That's too vague for me to guess. What packets are getting lost? >> > > > > >> > > > > On Thu, Jul 23, 2015 at 04:10:14PM -0700, Xuemei Liu wrote: >> > > > > > Hi, Ben, >> > > > > > >> > > > > > I tried your method, but the switch seems to drop some packets, >> as it >> > > > > does >> > > > > > not output the expected packets that I forward to send to it. >> Any >> > > advice? >> > > > > > >> > > > > > Thanks, >> > > > > > Xuemei >> > > > > > >> > > > > > On Thu, Jul 23, 2015 at 10:19 AM, Xuemei Liu < >> lxuemei3...@gmail.com> >> > > > > wrote: >> > > > > > >> > > > > > > Hi, Ben, >> > > > > > > >> > > > > > > Thanks for your response. >> > > > > > > "You realize that this will be terrible for performance, >> right?" >> > > > > > > In fact, I have not got all packets sent to user space. That >> is the >> > > > > > > problem I am facing now. I think performance might be another >> > > problem >> > > > > after >> > > > > > > I can receive all packet in user space. >> > > > > > > >> > > > > > > Thanks, >> > > > > > > Xuemei >> > > > > > > >> > > > > > > On Thu, Jul 23, 2015 at 10:13 AM, Ben Pfaff <b...@nicira.com> >> >> > > wrote: >> > > > > > > >> > > > > > >> On Thu, Jul 23, 2015 at 10:04:23AM -0700, Xuemei Liu wrote: >> > > > > > >> > I am new to ovs, and I am trying to send all packets from >> kernel >> > > > > space >> > > > > > >> to >> > > > > > >> > user space. I comment the "unlikely(!flow)" in >> > > datapath/datapath.c. >> > > > > > >> > However, it seems I just receive the first packet of each >> flow >> > > (the >> > > > > > >> first >> > > > > > >> > packet that match one forwarding rule in the bridge) in >> user >> > > space. >> > > > > > >> Could >> > > > > > >> > anyone tell me why? and is there other way to achieve my >> goal? >> > > > > > >> >> > > > > > >> You realize that this will be terrible for performance, >> right? >> > > > > > >> >> > > > > > >> It's kind of a waste to modify the kernel module for this. >> I'd >> > > just >> > > > > > >> modify userspace to send all packets to userspace, something >> like >> > > > > this: >> > > > > > >> >> > > > > > >> diff --git a/ofproto/ofproto-dpif-xlate.c >> > > > > b/ofproto/ofproto-dpif-xlate.c >> > > > > > >> index 52395a7..a98406a 100644 >> > > > > > >> --- a/ofproto/ofproto-dpif-xlate.c >> > > > > > >> +++ b/ofproto/ofproto-dpif-xlate.c >> > > > > > >> @@ -4777,7 +4777,7 @@ xlate_actions(struct xlate_in *xin, >> struct >> > > > > > >> xlate_out *xout) >> > > > > > >> >> > > > > > >> ctx.xin = xin; >> > > > > > >> ctx.xout = xout; >> > > > > > >> - ctx.xout->slow = 0; >> > > > > > >> + ctx.xout->slow = SLOW_ACTION; >> > > > > > >> ctx.xout->has_learn = false; >> > > > > > >> ctx.xout->has_normal = false; >> > > > > > >> ctx.xout->has_fin_timeout = false; >> > > > > > >> >> > > > > > > >> > > > > > > >> > > > > >> > > >> > >
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