I am using a Intel Corp. 82547EI Gigabit Ethernet Controller (LOM) network card with the e1000 driver in a PC used as a router. The link connected to this interface is 100 mbit. The tx and rx ring buffers are 256 by default in the e1000 driver. The minimum that they can be changed to by ethtool is 80. By having such a large ring buffer on a 100mbit link, there is a lot of delay introduced when link utilisation is at 100mbit and queueing takes place. When the tx ring buffer is 256 a delay of 30ms is introduced, this is reduced to 10ms by setting the TX ring buffer to 80. I reduced the tx ring buffer to 16, which is used by 3c59x driver as its tx ring buffer, and although this reduced the delay, the throughput was reduced as well. When im measuring delay the maximum queue size is 10 packets which would take 1ms to transmit when all 10 packets are MTU sized. Does anyone know the the optimal tx ring buffer for this driver when using a 100mbit link, or has anone experimented with it ? Jonathan - : send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
