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AIX Versions 3.2 and 4 Asynchronous Communications Guide

Performance Tuning

The device driver software is configured to give the best performance under the widest variety of conditions. Performance under certain conditions can be improved through the use of tunable parameters. As with most tunable parameters, increasing performance in one area decreases performance in other areas. The software supports a number of tunable parameters that may be useful under special conditions. These parameters are tunable on a per-port basis and can be set with stty-cxma, chdev, or SMIT.

EDELAY is a tunable parameter used to determine the number of milliseconds of delay between the time the first character arrives after a period of no characters and notification of its arrival to the host. This is also referred to as the wakeup rate between the host software Front End Process Operating System (FEPOS) and the host device driver. This has the advantage of reducing host overhead by allowing the host to process larger blocks of incoming data. Larger EDELAY values result in more characters being sent in a given time period. This will reduce host processor utilization and character response time and increase overall system throughput. Smaller EDELAY values result in fewer characters being sent in a given time period. This increases character response time and increases host processor utilization. The default value for EDELAY is 100.

This is a good value for normal tty activity including typing and UUCP. For applications receiving continuous input at high speeds, increasing EDELAY results in lower host overhead and an increase in overall system throughput. A value of 250 is reasonable.

Note: For more terminal options, see "Setting Terminal Options with stty-cxma" .

Related Information

For additional information about error messages and error logging, see:

The errdemon daemon.

The errclear command, errdead command, errlogger command, errpt command, errstop command.

Error Logging Overview in AIX Version 4.3 Problem Solving Guide and Reference.

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