3

I'm trying to diagnose intermittent poor wifi performance on my laptop, which has a fresh installation of 13.04.

I installed several network monitoring tools, including "slurm", which I'm now using to monitor both the wireless interface (wlan0) and the loopback interface (lo). The wireless interface, predictably, shows the same information displayed in the System Monitor; data generally flows at the rate of several hundred KB/second. The loopback interface, however, consistently shows a transaction speed of 5-40 KB/sec, maxing out at around 80-90. I don't really understand how Ubuntu's network interfaces work (plus the complexities of how they interact with Network Manager). Is it normal for the lo interface to be so slow? How does the loopback interface affect networking performance? Can I pretty much ignore it when trying to figure out my wifi problem?

Braiam
  • 69,112
Sam Lichtenstein
  • 133

1 Answers1

3

As soulsource already pointed out, you're probably looking at interprocess communication done over the localhost network. That isn't very efficient, but in programming this is sometimes useful to have a single piece of code whether the two components are running on the same machine or over the network. Let's have a look how to track this down.

As your tcpdump shows it's sending data to port 8332 on localhost, you can see what's listening there using netstat:

sudo netstat -nlptu | grep 8332

(-n for numeric output, -l for listening sockets, -p to show the process, -t and -u to show both TCP and UDP sockets.)

You should see something like 

tcp   0      0 127.0.0.1:8332   0.0.0.0:*   LISTEN     21891/SomeProcessName

Then investigate this process ID further:

ps u --pid 21891

This will show something like

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
gert     21891  0.0  0.0 480768 13836 ?        Sl   13:49   0:11 /path/to/some/binary

There.

How does the loopback interface affect networking performance? Can I pretty much ignore it when trying to figure out my wifi problem?

This has nothing to do with the performance over other network interface cards. I suggest to ask a new question for that.

Community
  • 1
gertvdijk
  • 69,427