Subject: pci/fxp performance quirks
To: None <firstname.lastname@example.org>
From: Hal Murray <email@example.com>
Date: 08/12/1999 23:28:43
> It could be, but we at pdq.com also tried fxp cards, and had
> the *same* problems. It would then be true only if the fxp
> also played with the same parameters.
Speaking of fxp... [I gave up on Tulips a while ago.]
I have two pairs of machines. The first pair has 400 MHz Intel/Celeron
CPUs. The second pair has 600 MHz Alpha/EV56 CPUs (Miata).
Each machine has a quad ethernet card: 21154 PCI-PCI bridge and Intel
82558 Ethernet chips. All are running vanilla 1.4.
If I run some quick tests that send a lot of network traffic, everything
looks reasonable on the Intel boxes.
On the Alphas, I see strange performance quirks. It never hangs,
just sometimes/often doesn't go as fast as I expect. I see things
like this in /var/log/messages:
Aug 12 19:12:47 mckinley /netbsd: fxp1: device timeout
Aug 12 19:13:28 mckinley last message repeated 5 times
Aug 12 19:13:43 mckinley last message repeated 2 times
Aug 12 19:15:39 mckinley /netbsd: fxp2: device timeout
Aug 12 19:17:50 mckinley /netbsd: fxp2: device timeout
An occasional delay of a second or three would explain the numbers
my test program is printing.
This happens much more often when actually transfering data in both
directions at the same time (on a full duplex link). It does happen
occasionally on a half duplex link.
One difference that might be interesting is that the quad ethernet
cards on the Alpha are plugged into a 64 bit PCI slot.
I've been trying on and off for the past hour or three to provoke
something similar on the Intel boxes. I haven't been able to do
it. That's not to say there isn't a problem, just that it's either
a lot harder to provoke or I don't know the secret yet.