Messages in this thread |  | | From | Christian Widmer <> | Subject | unnecessary retransmit from network stack | Date | Fri, 5 Oct 2001 14:29:53 +0200 |
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i wrote a prototype for a nic driver for my theses some time ago. when looking at the performance of my nic driver i could not beleave how slow it is. i started to log tcp sequence numbers and saw that the network stack asks my driver to transmit the same tcp paket multiple times within less then 2ms. how can that happen? below you see what the drivers sees when an ssh connection is set up on a PII 400MHz 2.4.7 kernel.
why does net_dev.hard_start_xmit get called multiple times with the same tcp packet?
TxMit: transmit function of the nic driver TxIrq: packet transmission reported by nic RxIrq: packet reception reported by nic
cpu clock-tick | event | Tcp SeqNo | Tcp AckNo ---------------|-------|-----------|---------- 0x186dce194bc8 | TxMit | 909902971 | 0 0x186dce1beb05 | TxIrq | 909902971 | 0 0x186dce1ef8f8 | RxIrq | 897283491 | 909902972 0x186dce1f8b03 | TxMit | 909902972 | 897283492 0x186dce220317 | TxIrq | 909902972 | 897283492 0x186dce3002e8 | RxIrq | 897283492 | 909902972 0x186dce308560 | TxMit | 909902972 | 897283515 <- dublicate 0x186dce330bab | TxIrq | 909902972 | 897283515 0x186dce3c09bf | TxMit | 909902972 | 897283515 <- dublicate 0x186dce3e9b6f | TxIrq | 909902972 | 897283515 0x186dce424310 | RxIrq | 897283515 | 909902994 0x186dce47bc44 | RxIrq | 897283515 | 909902994 0x186dcf094683 | TxMit | 909902994 | 897283791 0x186dcf0bcafb | TxIrq | 909902994 | 897283791
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