> I have a 2.1.128 box connected via PPP to a 2.0.35 box. Today I was
> hammering quite heavyly the 2.1.128 box and as the system load went
> up I started to see that packages transmitted over the PPP link
> started to get lost.
> I was torturing the 2.1.128 by doing "dd if=/dev/hdc of=/dev/null"
> (where /dev/hdc is my CD-ROM) and at the same time a "find
> /usr/src/linux -type -exec cp {} /dev/null \;". This seems to generate
> an interrupt storm (/usr/src/ is mounted on ide0, and obviously,
> /dev/hdc is on ide1).
> To test the PPP link I pinged the PPP host on the other side (the
> 2.0.35 box) and got this:
> 41 packets transmitted, 10 packets received, 75% packet loss
> even though I saw the modem lights flashing for both transmit and
> receive (this leads me to think that the TCP stack was indeed sending
> the ICMP packets, the remote host was responding to the ICMP echo but
> the TCP stack was not processing the recived packets).
> As soon as I killed the processes that were drowning the system the
> PING's started to como back and forth with no packet loss.
> This is a Pentium 75 box so I guess you won't be able to reproduce
> this if you have a lot of computer power and fast hardware.
Hm. I have Pentium233MMX and the same behaviour even with one IDE drive :-)
With both 2.0.35 and 2.1.90-2.1.126 ...
> My question is: is this the normal behavior for a system that is
> being heavyly hammered like this? Am I pushing this hardware to its
> limits, or there is somekind of problem in the TCP stack?
AFAIK this is problem with serial port design and IDE design. Try to use
'hdparm -u 1' (if you are brave enough: this is declared to be dangerous!).
I'm have packet loss without 'hdparm -u 1' with heavy activity on FAT32
partition but no packet loss even with extremal IDE activity with
'hdparm -u 1' for last year. Also no data corription was noted for the same
year with 'hdparm -u 1' but YMMV.
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