Hi, all, Following Ben's advice, I can forward all packets from kernel space to userspace. However, the performance of handling packets in userspace is not good enough. I read the code and find threads are used to handle the userspace upcalls (in ofproto/ofproto-dpif-upcall.c, function udpif_set_thread() ). According to the code, the number of threads should be adjustable. What I track from the code is shown below (in bridge.c), but I don't know where to set the number of threads. Could you give me some hint if possible? [image: Inline image 1]
Thanks, Xuemei On Fri, Jul 24, 2015 at 1:24 PM, Ben Pfaff <[email protected]> wrote: > It doesn't sound like you have a bottleneck, if CPU is less than 10%, so > I don't understand the question. > > On Fri, Jul 24, 2015 at 09:42:05AM -0700, Xuemei Liu wrote: > > 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 <[email protected]> > wrote: > > > > > Thanks very much Ben. > > > > > > On Fri, Jul 24, 2015 at 9:25 AM, Ben Pfaff <[email protected]> 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 <[email protected]> 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 <[email protected]> > 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 < > > >> [email protected]> > > >> > > > > 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 < > [email protected]> > > >> > > >> > > 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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