Re[3]: tcp_window_scaling degrades performance

[Maciej Soltysiak]

AK>> It's pretty easy for you to find out. Do a tcpdump -v or ethereal -v
AK>> from both the side of a host you download from and from the linux side.
AK>> Then compare all packets. If they don't match the firewall is 
AK>> doing something bad. Especially check window values and TCP options
AK>> in the SYN packets
MS> I will do that for sure, but preliminary investigation shows that
MS> this behaviour does not show with 2.6.7 and earlier, but appears for sure in
MS> 2.6.7-bk13 (Haven't tried earlier bk snapshots)
I seem to have isolated the changeset that causes my machines to have
very slow throughput, even as low as 2kB/s when tcp_window_scaling is
enabled.

http://linux.bkbits.net:8080/linux-2.6/cset@xxxxxxxxxxx?nav=index.html|ChangeSet@-3w
[TCP]: TCP acts like it is always out of memory.

Signed-off-by: Stephen Hemminger <shemminger@xxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxx>

Stephen, David, could you review this changeset, figure out possible
causes or suggest more methods for me to analyse this problem ?

Note that I am not saying that window_scaling is badly implemented,
but it just seems related.

Regards,
Maciej


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