Performance Tuning: Latency

Use this procedure to tune your AccelePort SCO UnixWare device driver for reduced latency. For a definition and general discussion of latency, see About Latency.

The SCO UnixWare device driver has interrupts disabled by default; this procedure will enable the interrupts and adjust the interrupt polling period-- the delay between a character's appearance in the adapter's buffers and the transmission of that character from the adapter to the operating system.

Start by setting the polling period to 10 milliseconds. To further reduce the latency of character reception, try smaller integer values until you are satisfied with the results. Note that reducing the polling period correspondingly increases system overhead, and may impact overall system performance. The minimum polling period is 1 millisecond. Setting a value of 0 disables interrupts.

Procedure

1. Run the SCO UnixWare network configuration utility by entering the following command:

   netcfg

2. Go to the advanced properties page for your AccelePort adapter and change the Interrupt Period from 0 to 10. This enables interrupts and sets the polling period to 10 milliseconds.
3. Save the file and exit from the editor.
4. Restart SCO UnixWare to effect the change.
5. If the latency is still too great, try smaller integer values (1 millisecond is the shortest supported polling period) until an acceptable latency is achieved.