where is k_compat.h?

[James Ralston]

On Wed, 2 Feb 2000, Paul Edwardson wrote:
> I have a 3C905B-TX-NM in a 733 Mhz Pentium III.  Even with both the
> NIC and the connected switch configured for 100BaseTX and full
> duplex (to eliminate the possibility of auto-negotiate problems) the
> connection slows to a creep then stalls in moderately heavy traffic.

Moderately heavy traffic to where?  To a machine on the same switch,
elsewhere on your LAN, or elsewhere in the world?

What types of connections slow to a creep and then stall?  TCP/IP
connections, all IP connections, or all connections of any type?

I ask because I have a tentative theory that the TCP/IP stack in
recent Linux kernels has a pathological case where throughput becomes
abysmal, and one of the situations where this seems to occur is with
two machines connected to the same switch talking to each other as
fast as they can in full duplex.

I'm still testing, so I'm reluctant to make any concrete statements,
but you might want to try one or more of the following things:

    Try turning off the RFC1323/RFC2018 features of the Linux 2.2.*
    kernel, by doing the following:

        # cd /proc/sys/net/ipv4
        # echo 0 >tcp_sack
        # echo 0 >tcp_timestamps
        # echo 0 >tcp_window_scaling

    I suspect doing so will prevent the connection from stalling
    entirely, but the throughput will probably still slow to a crawl.

    Try forcing both the switch and the NIC to half duplex mode.  In
    my limited testing, I've found that if I force the NIC of the
    machine that is *sending* the data to half duplex, the performance
    problems mostly vanish.

I'd be very curious to know what results you see...

Regards,
James

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