HP (Hewlett-Packard) 100BASE-TX Benutzerhandbuch

Troubleshooting 10/100Base-TX/9000

are in the transmit FIFO.

While the current Transmit Threshold value allows the PCI 100BT
product to achieve it's best performance, it also increases the probability
of Transmit Underrun errors.  A large number of Transmit Underrun
errors (more than 1 out of every 1000 packets) can cause a noticeable
drop in networking performance.Transmit Underrun errors may occur
when there is sufficient bus contention from competing I/O devices.
These errors can be monitored in two ways:

1. Examine the output from the

 command. If

the number of output errors is high (more than 1 out of every X
packets) then the system is most likely suffering from transmit
underruns on the specified network interface and corrective action
must be taken to resolve the problem.

2. Turn on nettl errors and warnings for the network interface being

monitored. The following command will turn on disasters, errors and
warnings for the network interface with Instance number 1. (NOTE:
It is highly recommended to always keep disasters and errors
enabled).

The nettl log file (by default is called /var/adm/nettl.LOG00) should then
be monitored for the following message:

HPPCI 10/100Base-T driver encountered a Transmit Underflow

If a significant number of these messages occur, and the timestamps for
each of the messages are within 30 seconds of each other, then the
specified networking interface will suffer a noticeable performance drop.
Corrective action must be taken to resolve this problem.

The PCI 100BT product supports 3 levels of Transmit Threshold.  These
3 levels are modified via the -S option of the lanadmin command as
follows:

lanadmin -S TransmitThreshold nmid

where:

a TransmitThreshold of 1024 is somewhat aggressive

a TransmitThreshold of 512 is most aggressive