20% packet loss with re0 in gigE mode vs. 0% in 100BT

Sean McNeil sean at mcneil.com
Mon Oct 11 13:09:08 PDT 2004

On Mon, 2004-10-11 at 12:31, Robert Watson wrote:
> On Mon, 11 Oct 2004, Sean McNeil wrote:
> > > Assuming you're not filling the send buffer, it would definitely suggest a
> > > driver, configuration, or hardware bug.  There have recently been a number
> > > of changes to the if_re driver to fix support for jumbo frames, etc.  It
> > > would be interesting to know whether backing out to earlier revisions of
> > > the if_re driver affect the problem you're seeing.  In particular,
> > > ifre.c:1.35 was the jumbo frame change, so 1.34 would be interesting, and
> > > 1.31 is before some other related changes.  Likewise, you could try
> > > backing out to before locking was introduced by setting debug.mpsafenet=0
> > > in loader.conf and then backing out to if_re.c:1.29.  I might be generally
> > > useful to try setting debug.mpsafenet=0 with the current driver to
> > > eliminate that as a possible concern.
> > 
> > These are good suggestions as well, but I have heard from another user
> > that has seen this kind of thing over all of these versions.  It is less
> > likely then that the jumbo or locking changes caused the issue. 
> Have you tried 4.x to see if the same problem occurs there?
> Have you tried the normal juggling of ACPI, APIC, and other configuration
> variables?  It sounds like things work fine at minimal bandwidth rates, so
> that probably rules out interrupt problems and the like, but I figured it
> was worth asking.
> I assume you've probably looked at substituting the switch, forcing
> auto-negotiation to 1gb, etc?

Again, I have failed to provide information that was sent in previous
emails under a different topic.  I haven't tried 4.x, no, but I have
tried with various configurations:

FreeBSD/re0/amd64/gigE fails
FreeBSD/re0/amd64/100BT passes
WinXP/re0/gigE passes
WinXP/dc0/100BT passes

Everything I have tested works just fine.  It is only when the re0 under
FreeBSD is using PHY gigE that I have any packet loss.  There is a small
chance that there is bursting that is causing the loss but I doubt it as
the output rate is 15Mbps.  This is a pretty low rate and not very
likely to cause serious bursting.

I now have a source stream and a saved stream from a receiver.  I will
attempt to examine the differences in them to see if it is just a matter
of some packets being dropped or if it is more nefarious.


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