[Beowulf] Re: typical latencies for gigabit ethernet

[Dave Love]

Gerry Creager <gerry.creager at tamu.edu> writes:

> Can you say something about any tuning you did to get decent results? 

To get the lowest latency, turn off rx interrupt coalescence, either
with ethtool or module parameters, depending on the driver.  Of course,
you may not want to turn it off completely, depending on how much load
the extra interrupts cause.

> We've had some interesting problems (until lately; new broadcom drivers 
> helped) getting decent performance.  We're using Dell 1950's with 
> Harpertown and broadcom NICs are native.
>
> Which driver parms had to get tweaked?

There are (at least) two different drivers for Broadcoms, and I've no
idea what that hardware has.  I've only used tg3, and am actually
somewhat confused by it.  (I haven't had time to try to understand the
driver code and I'm not primarily interested in those NICs as the
nVidias on our boxes seem better.)  Are you using tg3 or bnx2?