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SubjectRe: 2.6.17: slow (as hell) tcp inbound transfers
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Date
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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