[arch-general] [kernel26 >= .30 + e100] Slow ethernet

[Gerhard Brauer]

Hi,

since 2.6.30.x (i could not exactly say if also with the latest
2.6.29.x) stock kernels i have a terrible slow ethernet transfer rate on
my old Thinkpad T22 (Intel EtherExpress PRO/100 SP, module e100).

Normal transfer rate ex. to a mirror is for me ~700Kb/s but i got only
~80-90 Kb/s. And a bunch of RX overruns and frame errors.

I could solve it by following workarounds:
a) Disable ACPI (acpi=off), but this is the ugliest workaround.

b) When i generate CPU-Load (ex: dd if=/dev/zero of=/dev/null) the
transfer rate goes immediately up to normal and the RX error rate
increasing stops. Stopping the dd the rate goes down again. So i thought
it could be a timer/IRQ problem.
I tried different acpi= and pci= kernel parameters without success. Also
tried to isolate the Ethernet device to a non-shared IRQ.

c) Current working solution is if i use nohz=off as kernel param.
But testing with an 2.6.28 kernel i have installed on this TP there is
CONFIG_NO_HZ=y also set (diff is only that this kernel has
CONFIG_HZ=1000 and 2.6.30/31 CONFIG_HZ=300, but AFAIK if bootet with
NOHZ these settings are ignored (tickless)).

So there must be a signifikant change in >= 2.6.30 (tested 2.6.31 from
testing also). Anyone has an idea to solve it without nohz parameter? I
also could report it to LKML if this seems a bug (for me it is).

Regards
	Gerhard