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    SubjectRe: loopback behaviour under high load ...
    On Wed, 2 Apr 2003, Martin Josefsson wrote:

    > On Wed, 2003-04-02 at 18:23, Davide Libenzi wrote:
    > > On Tue, 1 Apr 2003, Davide Libenzi wrote:
    > >
    > > > And netstat shows Recv-Q=0 for the server socket, and Send-Q=N for the
    > > > client socket. This has been tested on 2.5.66 vanilla.
    > >
    > > An update on this. Kernel 2.4.20+epoll does not have this problem.
    >
    > I see something similar with 2.5.64-bk10 (seen with earlier 2.5 kernels
    > as well).
    >
    > I use distcc on my machine which is running 2.5.64-bk10 and using two
    > remote servers running 2.4.20 to do the compiling.
    >
    > Sometimes I see a ~120s stall in the middle of a connection with
    > Recv-Q=0 on the server (2.4.20) and Send-Q=N on the client (2.5.64-bk10)
    > (it's the client that's sending data to the server)
    >
    > x.x.x.x = client
    > y.y.y.y = server
    >
    > As you can see there's a long delay between 16:02:09 and 16:04:24
    >
    > There's some packetloss here (probably a congested interface in the
    > router on the way). The dump was made on the client.

    Hmm, we don't see any dropped packet at interface ( loopback ) level here:

    $ cat /proc/net/softnet_stat
    002a0c14 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

    $ ifconfig
    lo Link encap:Local Loopback
    inet addr:127.0.0.1 Mask:255.0.0.0
    UP LOOPBACK RUNNING MTU:16436 Metric:1
    RX packets:1349417 errors:0 dropped:0 overruns:0 frame:0
    TX packets:1349417 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:0




    - Davide

    -
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