April 22 Driver RuleZ

[Andrew Morton]

Matt Benjamin wrote:
> 
> Yes, on one of our three machines, we were seeing _glacially slow_
> transfer rates for some protocols, incl. ftp.  Speedup was 1000%.

If this was on a hubbed LAN (half-duplex) then you were quite possibly
getting duplex problems.

If a machine sends TCP at 10% wirespeed and receives TCP at wirespeed
then it's a fair bet that it's trying to do FDX when it should be doing
HDX.  I guess because the outgoing data is colliding with the incoming
ACKs.

The 3c59x/3c905B combo seems to get a _lot_ of collisions.  I have such
a machine at work and under kernel 2.2.9 I often see the collision count
at 25% of the Tx packet total.  Something I've been meaning to look
into.

> Note that one of the _other_ boomerang setups has the quiescing nic
> problem.  We haven't updated that one to the new driver, as we didn't see
> any sign the problem had yet been addressed.  When we can take it offline,
> though, we'll probably update just to improve throughput.  (Although
> _that_ machine didn't show noticable throughput problems.)

The foggy consensus seems to be that the sleepy NIC problem is caused by
the upstream switch deciding that the NIC has gone off the air.  One
would have to sniff the switch's port to verify this.  Or bug the
vendor...

NT and W9x won't show the problem because they're always chatting with
the domain controllers.


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-akpm-
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