Re: Thread+network crashes in 2.0/2.1

Larry McVoy (lm@who.net)
Sat, 28 Feb 1998 22:18:38 -0800

: >On Sat, 28 Feb 1998, Linus Torvalds wrote:
: >>
: >> In particular, I'd suggest trying the Intel EtherExpress Pro 100B if you
: >> need 100Mbps networking: it happens to be what I have, and it has been
: >> extremely stable here at Transmeta (the de4x5 cards we used before that
: >> were stable but had very bad noise problems over the cable that resulted
: >> in bad performance for everybody on the same net, so we ended up chucking
: >> them out the window: the problem seemed to be with the 21140 chip iself as
: >> we tried different cards with the same chip and we tried both drivers with
: >> the same results).
: >
: > Did this happen to manifest itself as 'Oversized packet ....'
: > messages ? I am keenly interested in the possibility .
: > although I am not using de4x5 cards , I am using the Kingston
: > variant here. At present not at 100mbps.
:
: No, the problems we had with the 21140 was that our routers reported
: excessive number of "runt" packets - there seemed to be something fishy
: with the collision handling of the cards or similar. The Linux machines
: themselves never reported anything really wrong, they just showed bad
: performance.
:
: It seemed to be mainly an issue when the network was under heavy load
: anyway (the cards seemed fine when load was low), and then it just got
: really bad rather quickly. We haven't seen the same kinds of problems
: with the eepro100 cards.

I can add some more data to this. I believe that the tulip (21140)
cards are very sensitive to cable quality and also that the cards vary in
quality even with in the same vendor/production run. Why, I have no idea.
But I routinely write and run tests to stress these cards (see bw_tcp.c in
lmbench, for example), and I've seen both excellent and awful performance
from pairs of tulip cards. I typically run in point to point mode as
well as full duplex, but I've tested through hubs as well as p-p in
half duplex. With a bad card in the mix it is virtually impossible to
break 6MB/sec. The problems don't seem to show up under light load at
all, except for maybe a delay sometimes when I rlogin to another machine
(I haven't figured out if that is a tulip or a linux problem).

Anyway, I concur with both points made by Linus: the tulip cards are
flakey under load and the eepro cards seem much better. It's too bad,
I liked the tulip cards when they came out, but they haven't stood up as
time has passed. Intel wins again. Sigh. Actually, only half a sigh,
Intel builds pretty nice stuff.

--lm

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