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    SubjectRe: 2.6.17: slow (as hell) tcp inbound transfers
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    Hi,

    On Mon, 2006-06-19 at 16:17 +0200, Vincent Vanackere wrote:
    > On 6/19/06, Brice Figureau <brice+lklm@daysofwonder.com> wrote:
    > > Now to the problem: I just finished the installation of a brand new
    > > 2.6.17 on a Dell PowerEdge 2850 which was running 2.6.16.19 really fine,
    > > and I'm encountering a strange issue.
    > >
    > > It seems that TCP inbound transfers (using either curl, or scp) are
    > > really slow except when issued on our gigabit LAN.
    >
    > Could you try the following to see if it cures your problem ?
    >
    > echo 0 > /proc/sys/net/ipv4/tcp_window_scaling

    Yes, that fixed it:
    # curl http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.17.tar.gz
    > /dev/null
    % Total % Received % Xferd Average Speed Time Time Time
    Current
    Dload Upload Total Spent Left
    Speed
    0 49.3M 0 9856 0 0 2991 0 4:48:05 0:00:03 4:48:02
    3680

    # echo 0 > /proc/sys/net/ipv4/tcp_window_scaling

    # curl http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.17.tar.gz
    > /dev/null
    % Total % Received % Xferd Average Speed Time Time Time
    Current
    Dload Upload Total Spent Left
    Speed
    1 49.3M 1 904k 0 0 86544 0 0:09:57 0:00:10 0:09:47
    71173

    Did something has changed between 2.6.16 and 2.6.17 regarding TCP window
    scaling ?

    I remember a discussion on lklm aroung 2.6.7 or so that finally ended as
    a bug in a firewall that wasn't handling TCP window scaling gracefully.
    That's certainly my case, I'll will have a look to that.

    Thanks for the help,
    --
    Brice Figureau

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