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    SubjectRe: [bug] stuck localhost TCP connections, v2.6.26-rc3+

    * Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> wrote:

    > > in terms of debugging there's not much i can do i'm afraid. It's not
    > > possible to get a tcpdump of this incident, given the extreme amount
    > > of load these testboxes handle.
    >
    > ...but you can still tcpdump that particular flow once the situation
    > is discovered to see if TCP still tries to do something, no? One needs
    > to tcpdump couple of minutes at minimum. Also please get /proc/net/tcp
    > for that flow around the same time.

    ok, will try those.

    > > One clue (which might or might not matter) is that distcc is one of
    > > the very few applications that makes use of sendfile().
    >
    > Can you please try with /proc/sys/net/ipv4/tcp_frto set to zero though
    > recv-q symptom seems weird would it be related to that (but there were
    > some recent fixes to FRTO and retrans_stamp change could have some
    > significance here)?
    >
    > Other than that, nothing since -rc1 seems suspicious to me (though I
    > hardly understand every part of networking).

    ok, i will first wait for it to trigger on a box and will do the tcpdump
    session (and /proc/net/tcp output), then i'll continue the tests with
    this done in the rc.local:

    echo 0 > /proc/sys/net/ipv4/tcp_frto

    and will see whether the hung connections still occur. The cycle of
    testing will be very slow i suspect.

    Ingo
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