em0: data transfer

[David Kirchner]

On 9/15/05, Alex Prokhorenko <freebsd-list at prokhorenko.net> wrote:
> Hello,
> 
> We have the following network card em0: <Intel(R) PRO/1000 Network
> Connection, Version - 1.7.35>  being controlled by 5.4-STABLE/SMP.
> The problem that we face lies in low data transfer speed from server
> to network. The card is connected to 100Mbps port of the switch
> (setting speed/duplex or autoselect option does not have any influence
> on the results). If there is a file downloaded via FTP from the server
> the speed is hardly higher than 4MBps. However, there is a flaw: if we
> launch trafshow -npi em0 outgoing transfer speed will immediately rise
> up to 12MBps, if we stop trafshow we get the low speed problem again: 4MBps.
> Please, help us locate the reason of such a low data transfer speed.

I can't state for a fact this is the problem, but I've found that
disabling ACPI in the kernel (and of course as a module) increases
transfer rates significantly.