slow writes on nfs with bge devices

[Kelly Yancey]

On Sun, 21 Jan 2007, Max Laier wrote:

> On Sunday 21 January 2007 13:25, Bruce Evans wrote:
> > 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?
>
> Did you look at the code in question?  It is concerned with fragmented
> packet chains (which NFS over UDP usually generated) and only commits to
> sending them, if there are enough descriptors available at once.  This
> can easily explain burstyness.
>
> Can you just try to disable the delayed checksums via "ifconfig -txcsum"?
> Should be an easy enough test.
>

  I realize that Bruce has already identified the problem as being with
the cabling, however I wanted to add a warning that disabling hardware
checksums for bge cards is not a good idea.  You can find my analysis of
data corruption bugs caused by using bge cards without checksum
offloading in the archives:
http://lists.freebsd.org/pipermail/freebsd-net/2004-January/002530.html

  Kelly

-- 
Kelly Yancey  -  kbyanc at posi.net | kelly at nttmcl.com