Subject: Re: e1000 full-duplex TCP performance well below wire speed

From: "Kok, Auke" <[email-masked]>
Date: Thu, 31 Jan 2008 10:47:42 -0800

Rick Jones wrote:
>> A lot of people tend to forget that the pci-express bus has enough
>> bandwidth on
>> first glance - 2.5gbit/sec for 1gbit of traffix, but apart from data
>> going over it
>> there is significant overhead going on: each packet requires transmit,
>> cleanup and
>> buffer transactions, and there are many irq register clears per second
>> (slow
>> ioread/writes). The transactions double for TCP ack processing, and
>> this all
>> accumulates and starts to introduce latency, higher cpu utilization
>> etc...
> 
> Sounds like tools to show PCI* bus utilization would be helpful...

that would be a hardware profiling thing and highly dependent on the part sticking
out of the slot, vendor bus implementation etc... Perhaps Intel has some tools for
this already but I personally do not know of any :/

Auke