Re: TCP transmit performance regression

Eric Dumazet
2012-07-05T10:42:05Z

On Thu, 2012-07-05 at 18:32 +0800, Ming Lei wrote:

> After testing on beagle-xm, the patch is good and network is OK, but
> iperf performance is still no improvement, see below:
>
> [root@root]#iperf -c 192.168.0.103 -w 131072 -t 10
> ------------------------------------------------------------
> Client connecting to 192.168.0.103, TCP port 5001
> TCP window size: 256 KByte (WARNING: requested 128 KByte)
> ------------------------------------------------------------
> [ 3] local 192.168.0.119 port 46776 connected with 192.168.0.103 port 5001
> [ ID] Interval Transfer Bandwidth
> [ 3] 0.0-10.0 sec 41.4 MBytes 34.7 Mbits/sec
>

I fear there are copies in the tx path as well, in smsc95xx_tx_fixup()

Could you add traces in this function to check if skb_copy_expand() is
called ?