Browse Prior Art Database

Optimized Work Station Controller Performance Based On Current Work Station Controller Workload Using a Closed Feedback Loop

IP.com Disclosure Number: IPCOM000101805D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 119K

Publishing Venue

IBM

Related People

Kiel, HG: AUTHOR [+3]

Abstract

Work Station Controllers (WSCs) support multiple Work Stations. Work stations can include displays, printers, or other types of devices. The WSC described in this disclosure can determine WSC processor utilization. WSC processor utilization is used to adjust polling rates to work stations, resulting in improved WSC performance. In general, if processor utilization is low, work stations are polled at a faster rate; if processor utilization is high, work stations are polled at a slower rate.

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Optimized Work Station Controller Performance Based On Current Work Station Controller Workload Using a Closed Feedback Loop

       Work Station Controllers (WSCs) support multiple Work
Stations.  Work stations can include displays, printers, or other
types of devices.  The WSC described in this disclosure can determine
WSC processor utilization.  WSC processor utilization is used to
adjust polling rates to work stations, resulting in improved WSC
performance.  In general, if processor utilization is low, work
stations are polled at a faster rate; if processor utilization is
high, work stations are polled at a slower rate.

      Work Station Controllers (WSCs) support multiple work stations
(W/S) attached using some type of W/S communication protocol.  W/S
can include displays, printers, or other devices.  The function of
the WSC is to process host data streams, translate and process
keystrokes, build formatted data streams to be sent to the host, etc.

      This disclosure is applicable to a W/S communication protocol
between the WSC and W/S where the WSC polls each W/S at some rate
checking for new status.  Several different types of polling may be
done by the WSC depending on the W/S type and what activity is taking
place.  Different types of polling may be done at different rates.
For example, two typical types of polling are:
-  Polling for a keystroke from a display (typical rates are 10 msec
to 30 msec).
-  Command completion polling:  after the WSC sends a command to a
W/S, the WSC will poll the W/S until the W/S indicates processing is
complete; typical rates are 1 msec to 6 msec).

      The rate of polling determines latency time:  the time from the
instant a W/S has new status until the WSC actually polls the W/S
allowing the W/S to indicate its new status. In some W/S
communication protocols, a W/S has no way to indicate new status
until it is polled by the WSC.  For example, if the polling rate
checking for command completion is 3 msec between polls, the average
latency time will be about 1.5 msec.

      The rate at which W/S are polled is set by WSC. Polling W/S at
a fast rate reduces latency time and service time (service time is
the measured time for a specific operation to complete when the
component being measured is without queueing).  However, polling at
fast rate will degrade performance on a heavily loaded WSC because of
increased W/S communication line utilization and/or increased WSC
processor utilization.  Utilization is the percentage of the time a
specific component is busy.

      This article describes how W/S polling rates are adjusted based
on processor utilization.  Processor utilization in the WSC can be
calculated using d...