Okay, great. The big change here is that we're actually setting up fewer of
those kernel flows on purpose to force them into userspace. Here's the commit
message that describes the change:
ofproto-dpif: Implement "flow setup governor" to speed up many short flows.
The cost of creating and initializing facets and subfacets and installing,
tracking, and uninstalling kernel flows is significant. When most flows
have only one or a few packets, this overhead is higher than the cost of
handling each packet individually. This commit introduces heuristics that
cheaply count (approximately) the number of packets seen in a flow and
skips most of this expensive bookkeeping until the packet count exceeds a
threshold (currently 5 packets).
So the fact that more packets are going to userspace is not bad and is, in
fact, expected. (There were also changes to make packet processing faster in
userspace.) It appears to be that you're not losing packets:
lookups: hit:117426873 missed:87741549 lost:0
In your previous message you were seeing a lot:
lookups: hit:3105457869 missed:792488043 lost:903955
That packet loss is bad, since it means that the packet was lost between kernel
and userspace, and it's gone forever. Obviously, there were a lot more packets
in that previous run, so we should monitor that over your full day run. You
said that you detected packet loss in your previous run. Are you still seeing
that?
At what rate are you running traffic? Are you still seeing 30% CPU for 20Mbps?
--Justin
On Jun 6, 2012, at 12:09 AM, Kaushal Shubhank wrote:
> Hi Justin, Oliver,
>
> So I switched to the newer version around 11 hrs ago. Here are some
> observations:
>
> 1. Number of flows has come down to a couple of thousands (from 12-15k).
> However we might wait for the setup to run for one whole day to see through
> peak and lean times and then count the flows again.
>
> 2. The flows have lesser percentage of lower packet count. I have attached a
> dump for reference.
>
> 3. The CPU usage is still around the same, that means we still see misses in
> kernel flow tables.
>
> $ sudo ovs-dpctl dump-flows br0 | grep -e "packets:[0123]," | wc -l
> 764
> $ sudo ovs-dpctl show
> system@br0:
> lookups: hit:117426873 missed:87741549 lost:0
> flows: 2145
> port 0: br0 (internal)
> port 1: eth3
> port 2: eth4
>
> - Kaushal
>
> On Tue, Jun 5, 2012 at 12:49 PM, Kaushal Shubhank <[email protected]> wrote:
> Surely we will try the 1.7.0 version. Considering this is production, we will
> be able to try this in off-peak hours. We will update you with the results as
> soon as possible.
>
> Thanks a lot and looking forward to contribute to the project in any way
> possible.
>
> Kaushal
>
>
> On Tue, Jun 5, 2012 at 12:36 PM, Justin Pettit <[email protected]> wrote:
> Of your nearly 12,000 flows, over 10,000 had fewer than four packets:
>
> [jpettit@timber-2 Desktop] grep -e "packets:[0123]," live_flows_20120604 |wc
> -l
> 10143
>
> Short-lived flows are really difficult for OVS, since there's a lot of
> overhead in setting up and maintaining the kernel flow table. We made
> *substantial* improvements for handling just this scenario in the forthcoming
> 1.7.0 release. The code should be stable, but it hasn't gone through a full
> QA regression. However, if you're willing to give it a shot, you can
> download a snapshot of the tip of the 1.7 branch:
>
> http://openvswitch.org/cgi-bin/gitweb.cgi?p=openvswitch;a=snapshot;h=04a67c083458784d1fed689bcb7ed904026d2352;sf=tgz
>
> We've only been able to test it with generated traffic, so seeing how much it
> improves performance with real traffic would be invaluable. If you're able
> to give it a try and let us know, we'd really appreciate it.
>
> --Justin
>
>
> On Jun 4, 2012, at 11:39 PM, Kaushal Shubhank wrote:
>
> > Hi Justin,
> >
> > This is how the connections are made, so I guess eth3 and eth4 are not in
> > the same network segment.
> > Router--->eth4==eth3--->switch
> >
> > We tried with eviction threshold 10000, but were seeing high packet losses.
> > I am pasting a few kernel flows (ovs-dpct dump-flows) here, and attaching
> > the whole dump (11k flows). I don't see any pattern. The port 80 filtering
> > flows were around 800 in the 11k flows, that means other flows were just
> > non-port 80 packets which we just send from eth3 to eth4 or vice-versa.
> >
> > If there is any way we reduce those (11k - 800) flows, we could reduce CPU
> > usage.
> >
> > in_port(1),eth(src=00:15:17:44:03:6e,dst=e8:b7:48:42:5b:09),eth_type(0x0800),ipv4(src=203.188.231.195,dst=1.2.138.199,proto=17,tos=0,ttl=127,frag
> > =no),udp(src=62294,dst=16464), packets:1, bytes:60, used:3.170s, actions:2
> > in_port(2),eth(src=e8:b7:48:42:5b:09,dst=00:15:17:44:03:6e),eth_type(0x0800),ipv4(src=94.194.158.115,dst=110.172.18.250,proto=6,tos=0,ttl=22,frag
> > =no),tcp(src=62760,dst=47868), packets:0, bytes:0, used:never, actions:1
> > in_port(1),eth(src=00:15:17:44:03:6e,dst=e8:b7:48:42:5b:09),eth_type(0x0800),ipv4(src=203.188.231.134,dst=209.85.148.139,proto=6,tos=0,ttl=126,frag=no),tcp(src=64741,dst=80),
> > packets:1, bytes:60, used:2.850s,
> > actions:set(eth(src=00:15:17:44:03:6e,dst=00:e0:ed:15:24:4a)),0
> > in_port(1),eth(src=00:15:17:44:03:6e,dst=e8:b7:48:42:5b:09),eth_type(0x0800),ipv4(src=110.172.18.137,dst=219.90.100.27,proto=6,tos=0,ttl=127,frag=no),tcp(src=49504,dst=12758),
> > packets:67603, bytes:4060369, used:0.360s, actions:2
> > in_port(2),eth(src=e8:b7:48:42:5b:09,dst=00:15:17:44:03:6e),eth_type(0x0800),ipv4(src=189.63.179.72,dst=203.188.231.195,proto=17,tos=0,ttl=110,frag=no),udp(src=60414,dst=16464),
> > packets:1, bytes:60, used:0.620s, actions:1
> > in_port(2),eth(src=e8:b7:48:42:5b:09,dst=00:15:17:44:03:6e),eth_type(0x0800),ipv4(src=213.57.230.226,dst=110.172.18.8,proto=17,tos=0,ttl=101,frag=no),udp(src=59274,dst=24844),
> > packets:0, bytes:0, used:never, actions:1
> > in_port(1),eth(src=00:15:17:44:03:6e,dst=e8:b7:48:42:5b:09),eth_type(0x0800),ipv4(src=195.35.128.105,dst=110.172.18.250,proto=6,tos=0,ttl=15,frag=no),tcp(src=54303,dst=47868),
> > packets:3, bytes:222, used:5.300s, actions:2
> > in_port(1),eth(src=00:15:17:44:03:6e,dst=e8:b7:48:42:5b:09),eth_type(0x0800),ipv4(src=110.172.18.154,dst=76.186.139.105,proto=6,tos=0,ttl=126,frag=no),tcp(src=10369,dst=61585),
> > packets:1, bytes:60, used:0.290s, actions:2
> > in_port(1),eth(src=00:15:17:44:03:6e,dst=e8:b7:48:42:5b:09),eth_type(0x0800),ipv4(src=78.92.118.9,dst=110.172.18.80,proto=17,tos=0,ttl=23,frag=no),udp(src=44779,dst=59357),
> > packets:0, bytes:0, used:never, actions:2
> > in_port(2),eth(src=e8:b7:48:42:5b:09,dst=00:15:17:44:03:6e),eth_type(0x0800),ipv4(src=89.216.130.134,dst=203.188.231.206,proto=17,tos=0,ttl=33,frag=no),udp(src=52342,dst=30291),
> > packets:0, bytes:0, used:never, actions:1
> > in_port(2),eth(src=e8:b7:48:42:5b:09,dst=00:15:17:44:03:6e),eth_type(0x0800),ipv4(src=76.226.72.157,dst=110.172.18.250,proto=6,tos=0,ttl=36,frag=no),tcp(src=46637,dst=47868),
> > packets:2, bytes:148, used:2.730s, actions:1
> > in_port(1),eth(src=00:15:17:44:03:6e,dst=e8:b7:48:42:5b:09),eth_type(0x0800),ipv4(src=89.211.162.95,dst=110.172.18.80,proto=17,tos=0,ttl=92,frag=no),udp(src=19442,dst=59357),
> > packets:0, bytes:0, used:never, actions:2
> > in_port(2),eth(src=e8:b7:48:42:5b:09,dst=00:15:17:44:03:6e),eth_type(0x0800),ipv4(src=86.179.231.157,dst=110.172.18.11,proto=17,tos=0,ttl=109,frag=no),udp(src=58240,dst=23813),
> > packets:7, bytes:1181, used:1.700s, actions:1
> > in_port(2),eth(src=e8:b7:48:42:5b:09,dst=00:15:17:44:03:6e),eth_type(0x0800),ipv4(src=72.201.71.66,dst=203.188.231.195,proto=17,tos=0,ttl=115,frag=no),udp(src=1025,dst=16464),
> > packets:1, bytes:60, used:2.620s, actions:1
> > in_port(1),eth(src=00:15:17:44:03:6e,dst=e8:b7:48:42:5b:09),eth_type(0x0800),ipv4(src=95.165.107.21,dst=110.172.18.80,proto=17,tos=0,ttl=96,frag=no),udp(src=49400,dst=59357),
> > packets:1, bytes:72, used:3.360s, actions:2
> > in_port(1),eth(src=00:15:17:44:03:6e,dst=e8:b7:48:42:5b:09),eth_type(0x0800),ipv4(src=110.172.18.203,dst=212.96.161.246,proto=6,tos=0,ttl=127,frag=no),tcp(src=49172,dst=80),
> > packets:2, bytes:735, used:0.240s,
> > actions:set(eth(src=00:15:17:44:03:6e,dst=00:e0:ed:15:24:4a)),0
> > in_port(0),eth(src=00:e0:ed:15:24:4a,dst=e8:b7:48:42:5b:09),eth_type(0x0800),ipv4(src=203.188.231.54,dst=111.119.15.31,proto=6,tos=0,ttl=64,frag=no),tcp(src=47463,dst=80),
> > packets:6, bytes:928, used:4.440s, actions:2
> >
> > Thanks,
> > Kaushal
> >
> > On Tue, Jun 5, 2012 at 11:29 AM, Justin Pettit <[email protected]> wrote:
> > Are eth3 and eth4 on the same network segment? If so, I'd guess you've
> > introduced a loop.
> >
> > I wouldn't recommend setting your evection threshold so high, since OVS is
> > going to have to do a lot of work to maintain so many kernel flows. I
> > wouldn't go above 10s of thousands of flows. What do your kernel flows
> > look like? You have too many to post here, but maybe you can provide a
> > sampling of a couple hundred. Do you see any patterns?
> >
> > --Justin
> >
> >
> > On Jun 4, 2012, at 10:40 PM, Kaushal Shubhank wrote:
> >
> > > Hello,
> > >
> > > We have a simple setup in which a server running a transparent proxy
> > > needs to intercept the http port 80 data. We have installed openvswitch
> > > (1.4.1) in the same server (running Ubuntu-natty 2.6.38-12-server 64bit)
> > > to feed the proxy with the corresponding type of packets while bridging
> > > all other types of packets. The functionality is working properly but the
> > > CPU usage is quite high (~30% for 20mbps traffic). The total load we need
> > > to deploy on is around 350mbps, and as soon as we plug in, the CPU usage
> > > shoots up to 100% (on a quad core Intel(R) Xeon(R) CPU E5420 @ 2.50GHz),
> > > even when only allowing all the packets to flow through br0. Packet loss
> > > also starts to occur.
> > >
> > > After reading similar discussions on previous threads I made my bridge
> > > stp-enabled and increased the flow-eviction-threshold to "1000000". Still
> > > the CPU load is high due to misses in kernel flow table. I have defined
> > > only the following flows:
> > >
> > > $ ovs-ofctl dump-flows br0
> > >
> > > NXST_FLOW reply (xid=0x4):
> > > cookie=0x0, duration=80105.621s, table=0, n_packets=61978784,
> > > n_bytes=7438892513, priority=100,tcp,in_port=1,tp_dst=80
> > > actions=mod_dl_dst:00:e0:ed:15:24:4a,LOCAL
> > > cookie=0x0, duration=80105.501s, table=0, n_packets=49343241,
> > > n_bytes=113922939324, priority=100,tcp,dl_src=00:e0:ed:15:24:4a,tp_src=80
> > > actions=output:1
> > > cookie=0x0, duration=518332.577s, table=0, n_packets=3052099665,
> > > n_bytes=2041603012562, priority=0 actions=NORMAL
> > > cookie=0x0, duration=80105.586s, table=0, n_packets=46209782,
> > > n_bytes=109671221356, priority=100,tcp,in_port=2,tp_src=80
> > > actions=mod_dl_dst:00:e0:ed:15:24:4a,LOCAL
> > > cookie=0x0, duration=80105.601s, table=0, n_packets=40389137,
> > > n_bytes=5660094662, priority=100,tcp,dl_src=00:e0:ed:15:24:4a,tp_dst=80
> > > actions=output:2
> > >
> > > where 00:e0:ed:15:24:4a is br0's MAC address
> > >
> > > $ ovs-dpctl show
> > >
> > > system@br0:
> > > lookups: hit:3105457869 missed:792488043 lost:903955 {these lost
> > > packets came with 350mbps load and do not change with 20mbps}
> > > flows: 12251
> > > port 0: br0 (internal)
> > > port 1: eth3
> > > port 2: eth4
> > >
> > > As far as we could understand, the missed packets here cause context
> > > switch to user-mode and increase CPU usage. Let me know if any other
> > > detail about the setup is required.
> > >
> > > Is there anything else we can do to reduce CPU usage?
> > > Can the flows above be improved in some way?
> > > Is there any other configuration for deployment in production that we
> > > missed?
> > >
> > > Regards,
> > > Kaushal
> > > _______________________________________________
> > > discuss mailing list
> > > [email protected]
> > > http://openvswitch.org/mailman/listinfo/discuss
> >
> >
> > <flows.tgz>
>
>
>
> <live_flows_20120606_1206>
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