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    SubjectRe: 3c59x problems solved -- mostly
    On Wed, Sep 27, 2000 at 11:26:09PM +1100, Andrew Morton wrote:
    > > Any suggestions to reduce those even further
    > > more than welcome, as I suppose this might cause some Multicast UDP
    > > packets to get dropped. :-/
    > Yes, you'll be dropping packets.

    Hmm... Not good.

    > > Would using SCSI instead of IDE help, do you think ?
    > It depends upon the SCSI driver. I haven't measured kernel interrupt
    > latencies for a while. Back in March, IDE beat the pants off SCSI in
    > this regard.
    > The IDE system was UDMA-66 (using hdparm -u1 -d1). The SCSI sytem was
    > from Advansys (I don't know how good this driver is). The numbers are
    > at This
    > was for the 2.3.99 kernel.
    > IDE: 27 usecs
    > SCSI: 42 usecs
    > Still, these aren't large enough to explain this behaviour.

    What we're seeing is we stress the hd's so much the whole system becomes
    terribly slow whenever a disk access is needed. Simply logging in on the
    console takes ages then. Perhaps this could explain those buffer
    overruns ?

    > Are you sending much output to the console? You'll see from Doug
    > Gilbert's numbers that the console driver can block interrupts for a
    > millisecond. Try running X, or otherwise prevent things from writing to
    > the console.

    Nope. Just X clients running on a remote X server.

    > The sensible alternative, of course, is to use a multicast filter. The
    > 3c905B/C does have a 256 slot hash filter. Unfortunately (and
    > uncharacteristically), 3com forgot to document it. However it _is_
    > implemented in 3com's own GPL'ed driver. This driver is bundled in
    > RedHat 6.x and is available at
    > . It's worth
    > visiting that site just for the amusement factor of having to click on
    > "I agree" for the license. It's the GPL!

    Thanks for the info. So the standard driver uses a software filter for
    multicasts then ? What does that mean ? Not promiscuous mode, I suppose ?

    > > The 2.2.17 driver still seems to have a few bugs though: we get messages
    > > like: "Too much work in interrupt, status e401". This seems to happen
    > > more on machines with RX buffer overruns.
    > hmm.. Yes, something is wrong. I see this could perhaps silently
    > happen if the driver is hopelessly out of memory. And this would
    > explain the failure you saw in the 2.2.16 driver. It had an
    > Rx-stops-working-on-OOM bug.
    > Could you please, before doing anything else, see if
    > echo '512 1024 1536' > /proc/sys/vm/freepages
    > makes a difference?

    I've been using '512 1024 2048' for the last series of tests. I suppose
    that's ok as well, or isn't it ?


    Arnaud Installe <>

    Q: What do you call a blind pre-historic animal?
    A: Diyathinkhesaurus.

    Q: What do you call a blind pre-historic animal with a dog?
    A: Diyathinkhesaurus Rex.
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