[CentOS] UDP Perfomance tuning

[Simon Matter]

> Hi,
>
> We are running on 5.5 on a HP ProLiant DL360 G6.
> Kernel version is 2.6.18-194.17.1.el5 (we had also tested with the latest
> available kernel kernel-2.6.18-238.1.1.el5.x86_64)
>
> We running some performance tests using the "iperf" utility.
>
> We are seeing very bad and inconsistent performance on the UDP testing.
>
> The maximum we could get, was 440 Mbits/sec, and it varies from 250 to 440
> Mbits/sec.

That hurts. So, what speed do you get using TCP? You should really get
almost wire speed with TCP, so I expect to be the same with UDP. I'm
usually testing raw TCP transfers with mbuffer listening on one side and
piping data to in using bash on the other side, like 'cat /dev/null >
/dev/tcp/host/port'

BTW, I have never used iperf, but is it sane to run it via strace? It will
for sure slow things down.

Simon

> We are connected on a 1000Mb/s link, we also tested the same using a
> cross-over connections between the two machines, but the same performance.
>
> We also see a lot of dropped UDP packets.
>
> Udp:
>     551522838 packets received
>     1902 packets to unknown port received.
>     109709802 packet receive errors
>     7239 packets sent
>
>
> We had checked all the kernel configurations and set them as recommended.
>
> This is the settings and tests we have done
>
> Server:
> net.core.rmem_default = 2097152
> net.core.wmem_default = 2097152
> net.core.rmem_max = 8388608
> net.core.wmem_max = 8388608
> strace -fttt -o /tmp/server.trace iperf -s -u -p 2222 -w 6m -i 5 -l 1k
>
> Client:
> net.core.rmem_default = 2097152
> net.core.wmem_default = 2097152
> net.core.rmem_max = 8388608
> net.core.wmem_max = 8388608
> strace -fttt -o /tmp/client.trace iperf -p 2222 -u -w 6m -i 5 -t 60 -c
> 192.168.1.2 -b 990M -l 1k
>
> Can someone please help me with this, since I am running in circles and
> can't get the required UDP performance?
>
> --
> Prasad Pillarisetti
> "If everything is coming your way, then you are in the wrong lane"
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