[ovs-discuss] High CPU Usage by ovs-vswitchd and resulting packet loss

Wed Jun 6 07:09:03 UTC 2012

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 at 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 <kshubhank at gmail.com>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 <jpettit at nicira.com> wrote:
>
>> Of your nearly 12,000 flows, over 10,000 had fewer than four packets:
>>
>> [jpettit at 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 <jpettit at nicira.com>
>> 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 at 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
>> > > discuss at openvswitch.org
>> > > http://openvswitch.org/mailman/listinfo/discuss
>> >
>> >
>> > <flows.tgz>
>>
>>
>
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