Re: ure0: Questionable Performance

[Greg Troxel <gdt%lexort.com@localhost>]

matthewd%fastmail.us@localhost writes:

I am amused by "older laptop" and "USB-C".  Those don't go together!  I
call anything new enough to have USB-C "relatively new".

> $ ifconfig ure0
> ure0: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         capabilities=0x3ff00<IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx,TCP4CSUM_Tx>
>         capabilities=0x3ff00<UDP4CSUM_Rx,UDP4CSUM_Tx,TCP6CSUM_Rx,TCP6CSUM_Tx>
>         capabilities=0x3ff00<UDP6CSUM_Rx,UDP6CSUM_Tx>
>         enabled=0
>         ec_capabilities=0x1<VLAN_MTU>
>         ec_enabled=0
>         address: 9c:eb:e8:54:53:73
>         media: Ethernet autoselect (1000baseT full-duplex)
>         status: active

> However, using iperf3 to measure networking performance, it seems a bit substandard:
>
> $ iperf3 -c 192.168.1.131
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-10.02  sec  55.4 MBytes  46.4 Mbits/sec    0             sender
> [  5]   0.00-10.24  sec  55.5 MBytes  45.4 Mbits/sec                  receiver

From other comments, it seems like this device is just not that good.

The only suggestions I would have to debug it are:

  - Test in UDP mode also.   TCP is extremely sensitive to loss.
    iperf/TCP measures how well you can do TCP which is what you usually
    care about, and if it's close to line rate (even 350/1000), you know
    all is well.  But if it's slow, you don't know if each packet is
    slow with little loss, or loss often, or loss above a certain rate,
    or ?

  - Look at "netstat -i" and error counters, and also do "netstat -s"
    before and after and diff them, on a system with nothing else
    happening (maybe even single user).  Anything that changes that you
    don't expect is interesting and I've found a lot of issues this way.

  - Run tcpdump and save to a file, and use tcpdump2xplot from
    graphics/xplot-devel to visualize it, after patching up the perl
    program or editing the trace to make it look like tcpdump used to
    look.  This is a lot of effort, and requires you to not only learn
    to deal with that software, but to really understand TCP.  But it
    can be very illuminating as to what is going on.

    You can also select one stream and just examine the text output.