Re: port-shark/57613: Abysmal network performance on shark

[Havard Eidnes <he%NetBSD.org@localhost>]

The following reply was made to PR port-shark/57613; it has been noted by GNATS.

From: Havard Eidnes <he%NetBSD.org@localhost>
To: herdware%sdf.org@localhost
Cc: gnats-bugs%netbsd.org@localhost
Subject: Re: port-shark/57613: Abysmal network performance on shark
Date: Sat, 16 Sep 2023 14:18:32 +0200 (CEST)

 > Well this is embarrassing. I took all the things you wanted and
 > tested two separate network switches. The problem turns out
 > that "mediaopt full-duplex" fubars everything. Don't even
 > remember that. I briefly tested this with netbsd-9 before going
 > to netbsd-10 and I can remember that network was pretty pants
 > on that too. Unsure of when that full-duplex was added
 > though. Removing full-duplex makes the net behave normally.
 >
 > FTR there was zero in the error counters even when using full-duplex.=
 
 
 Oh, ancient knowledge about 100Mbit/s ethernet and auto-
 negotiation status and results becomes useful again :)
 
 Setting the host to "static full-duplex" causes auto-negotiation
 to be disabled on the host, and *the other end* if it is set up
 to do auto-negotiation, will *by the spec* then need to fall back
 to half-duplex.  The half-duplex end will then end up seeing
 "jabber errors", i.e. the host "talking" while the local half-
 duplex end is also transmitting, so the half-duplex rules are not
 followed by the host (naturally).  It thus makes perfect sense
 that you do not see the resulting errors on the host doing
 full-duplex, as they will be seen on the switch end instead.
 
 So it *does* have an explanation...
 
 Configurations which are "OK":
 
 host       switch
 100M auto  100M auto   <-- recommended if supported
 100M FDX   100M FDX
 100M HDX   100M HDX
 100M HDX   100M auto
 100M auto  100M HDX
 
 Configurations which result in duplex-conflict, and are thus
 *not* OK:
 
 host       switch
 100M FDX   100M auto
 100M auto  100M FDX
 100M FDX   100M HDX
 100M HDX   100M FDX
 
 Regards,
 
 - H=E5vard