Adaptive polling system by generating sequence of polling signals whose magnitudes are functionally related to the occurrence of the busy signal

• US 5,566,351 A
• Filed: 06/20/1994
• Issued: 10/15/1996
• Est. Priority Date: 06/20/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Crittenden, John M., Schwendiman, Chris A.
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): Huang, Po C.
• Application Number:
  US08/262,703
• Time in Patent Office: 848 Days
• Field of Search: 177/25.11, 370/60, 370/84, 377/20, 455/58.1, 340/825.8, 395/114, 395/550, 395/868, 395/182.19, 395/835, 395/839, 364/130, 364/148, 364/166, 364/514 B
• US Class Current: 710/46
• CPC Class Codes: G06F 13/22 using successive scanning, e.g. polling G06F13/24 takes precedence

Abstract

System timers set by a central processing unit (CPU) provide a variable wait time functionally adapted and related to peripheral device availability. Wait time is iteratively and dynamically adjusted to more closely match peripheral performance to the system, thereby reducing CPU load and enhancing data throughput, with the data output routine executing at a process level rather than an interrupt level.

In a preferred embodiment, the prior wait time is cumulated during which the peripheral is unavailable for data in order to form a running average delay utilized as a starting point for a next data input. Large delays are weighted to avoid skewing average wait time too quickly for infrequent longer events. Data throughput is thereby increased, avoiding unnecessary dormant periods with no output from the system, while, at the same time, CPU loading is reduced by avoiding excessive system polling.

Claims

1. A method for controlling a peripheral device in a computer system having associated therewith ready signals and busy signals comprising:

generating a sequence of first polling signals defining a corresponding sequence of first intervals of decreasing magnitudes whose magnitudes are functionally related to frequency of occurrence of said busy signals, wherein a given one of said first intervals being determined from a running average of preceding ones of said first intervals;

executing status checks of said peripheral device with said first polling signals;

generating a sequence of second polling signals defining a corresponding sequence of second intervals of increasing magnitudes occurring after said first intervals, and wherein a given one of said second intervals is determined from a running average of preceding ones of said second intervals, said increasing magnitudes being functionally related to frequency of occurrence of said busy signals;

executing status checks of said peripheral device with said second polling signals;

generating a sequence of third polling signals defining a corresponding sequence of third intervals of constant magnitude occurring between said first and said third intervals functionally related to frequency of occurrence of said busy signals; and

executing status checks of said peripheral with said third polling signals.

2. The method of claim 1 wherein said third intervals occur between said first and said second intervals.

3. The method of claim 2 wherein said constant magnitude of said third intervals is predetermined.

4. The method of claim 3 wherein said constant magnitude of said third intervals is less than any of said decreasing and increasing magnitudes.

5. The method of claim 4 including generating a sequence of fourth polling signals after said sequence of second polling signals defining a corresponding sequence of fourth intervals of constant magnitude whose magnitude is functionally related to frequency of occurrence of said busy signals;

and

executing status checks of said peripheral with said fourth polling signals.

6. The method of claim 5 wherein said constant magnitude of said fourth intervals is predetermined.

7. The method of claim 5 wherein said constant magnitude of said fourth intervals is greater than said constant magnitude of said second intervals.

8. A method for efficient management of input-output in a computer system including a peripheral, comprising:

generating polling signals;

checking busy status of said peripheral;

monitoring prior delays associated with said busy status in response to said polling signals; and

adaptively generating subsequent polling signals at intervals functionally related to said monitoring;

and wherein said monitoring comprises detecting whether said peripheral device is in said busy status, and

A. when said busy status is detected,

A(1) updating statistical delay data;

A(2) computing a delay value; and

A(3) restarting a timer;

B. when said busy status is not detected,

B(1) outputting data to said device;

B(2) detecting whether additional said data is available for output;

B(3) when said additional data is detected as available for output, determining whether a prior delay associated with said busy status is less than a threshold;

B(3)a executing .step A if said prior delay is not less than said threshold; and

B(3)b executing step B(5) if said prior delay is less than said threshold;

B(4) when said additional data is detected as not available for output executing step B(5); and

B(5) re-activating a process executing on said system in response to step B(3)b or step B(4).

9. The method of claim 8 wherein said steps of computing and starting said timer further comprise:

D. detecting a first busy status since a last output to said peripheral device;

computing an average delay of said output to said peripheral device;

setting a wait period before said generating one of said subsequent polling signals comprised of a fraction of said average delays; and

executing step A(3);

E. detecting absence of a first busy status since a last output to said peripheral device;

E(1). detecting a preselected number of busy polls has occurred;

setting a wait period before said generating one of said next polling signals comprised of a product of a preceding said wait period and a predetermined number greater than zero; and

executing step A(3);

E(2). detecting absence of occurrence of a preselected number of busy polls;

setting a wait period before said generating one of said next polling signals comprised of a predetermined fraction of a preceding said wait period; and

executing step A(3).

10. A system for controlling a peripheral device in a computer system comprising:

means for generating a sequence of first polling signals defining a corresponding sequence of first intervals of decreasing magnitudes whose magnitudes are functionally related to frequency of occurrence of said busy signals, wherein a given one of said first intervals being determined from a running average of preceding ones of said first intervals;

means for executing status checks of said peripheral device with said first polling signals;

means for generating a sequence of second polling signals defining a corresponding sequence of second intervals occurring after said first intervals, said second intervals being of increasing magnitudes whose magnitudes are functionally related to frequency of occurrence of said busy signals;

means for executing status checks of said peripheral device with said second polling signals;

wherein a given one of said second intervals is determined from an average of preceding ones of said second intervals;

means for generating a sequence of third polling signals defining a corresponding sequence of third intervals of constant magnitude occurring between said first and said third intervals whose magnitudes are functionally related to frequency of occurrence of said busy signals; and

means for executing status checks of said peripheral with said third polling signals.