slow writes on nfs with bge devices

[Bruce Evans]

On Sun, 21 Jan 2007, Max Laier wrote:

> On Sunday 21 January 2007 07:25, Bruce Evans wrote:
>> nfs writes much less well with bge NICs than with other NICs (sk, fxp,
>
> Do you use hardware checksumming on the bge?  There is an XXX in
> bge_start_locked() that looks a bit suspicious to me.

I use the default for that.  Wouldn't checksum problems show up as errors
somwhere?

>>> [excessive quoting deleted]

tcpdump shows a lot of intervals between nfs write requests of almost
exactly 10 mS (even with HZ = 1000, but more obvious with HZ = 100)
for the broken case, so the problem is apparently related to timeouts,
or timeouts are masking a larger problem.  (The average interval between
write requests needs to be about 683 uS to avoid wasting any bandwith.
fxp <-> fxp on the same network averages 708 uS.  fxp <-> bge 5701
averages 3981.)

Bruce