Hello,
I'm having some curious bandwidth problems which I hope somebody can save
me from.
Two scenarios:
Scenario (1)
Two machines, directly connected via crossover, (100Mbit, full duplex).
Box 1: 333MHz K5 with a 'Lite-On Communications Inc LNE100TX'.
kernel: 2.4.8-19mdk
Box 2: 1GHz PIII with a '3c905C', kernel: 2.4.17
Running on box 1 is a simple tcp server spitting out lumps of data to
anybody who connects. On box 2 is a complementry client program to take
the data and throw it away.
In this configuration, I consistantly get get 10.98 Megabytes/second.
Scenario (2)
As before, except a third machine is inserted between the other two as a
gateway (again connected via crossover to both boxes).
Box 3: 700MHz C3 with two 'Intel Corporation 82557 [Ethernet Pro 100]',
kernel: 2.4.12-ac3
When the same client+server programs are run, I get 0.904 Megabytes/second.
----------
Obviously something is very wrong here, so we did some snooping.
We noticed we were getting a large number of buffer overruns on 'Box 3'.
(Transmit buffer on the interface connected to box 2 - client, and Receive
buffer on the interface connected to box 1 - server):
eth0 Link encap:Ethernet HWaddr 00:03:2D:00:25:43
inet addr:10.0.0.2 Bcast:10.255.255.255 Mask:255.0.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1208495 errors:0 dropped:0 overruns:4 frame:0
TX packets:2032372 errors:28 dropped:0 overruns:278 carrier:28
collisions:0 txqueuelen:100
Interrupt:12 Base address:0xe400 Memory:c8810000-c8810c40
eth1 Link encap:Ethernet HWaddr 00:03:2D:00:2D:07
inet addr:192.168.123.254 Bcast:192.168.123.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1933904 errors:0 dropped:0 overruns:27191 frame:0
TX packets:1107503 errors:0 dropped:0 overruns:1 carrier:0
collisions:0 txqueuelen:100
Interrupt:11 Base address:0xcc00 Memory:c8812000-c8812c40
(Interestingly, when we swaped the intel card in box 3 (eth1) for a realtek
FA310TX, we got no receive overruns, but frame errors instead -- still with
poor performance).
We tried using different cables - no change.
We increased/decreased the TxDescriptors and RxDescriptors variables in the
e100 driver - marginal change here, but never got more than 1.2 MB/sec
We tried the eepro100 driver instead of the e100 driver - no change.
The client and server programs can be found at:
http://developers.antefacto.net/~killian/linux-net/0.html
Thanks,
Killian.
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