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Browse Prior Art Database

Input/Output Load Balancing

IP.com Disclosure Number: IPCOM000079280D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 30K

Publishing Venue

IBM

Related People

Kenney, GQ: AUTHOR

Abstract

Balancing of loads on input/output (I/O) devices and channels contributes significantly to improved performance in the operation of computing systems. U. S. Patent No. 3,702,006 to Page describes a technique for load balancing, by counting the number of times each I/O device and channel is utilized by each task during time intervals between allocation routines. The load balancing technique presented herein involves the maintenance of, for example, Execute Channel Program (EXCP) counts for a device rather than a "number of users" count. The objectives of this technique are:

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Input/Output Load Balancing

Balancing of loads on input/output (I/O) devices and channels contributes significantly to improved performance in the operation of computing systems. U.
S. Patent No. 3,702,006 to Page describes a technique for load balancing, by counting the number of times each I/O device and channel is utilized by each task during time intervals between allocation routines. The load balancing technique presented herein involves the maintenance of, for example, Execute Channel Program (EXCP) counts for a device rather than a "number of users" count. The objectives of this technique are:

1) To allow for operation in an environment where simultaneous allocations are taking place, each unaware of the existence of the others.

2) To provide an acceptable I/O load balancing technique which is dependent upon information gathered and analyzed by direct-access device and channel only. This is to reduce the dependency on other system components and the main storage requirement for control blocks. Method of Gathering and Analyzing Information.

Two factors must be kept for each direct access device and channel in the system:

1. An Actual loading on the device (or channel), derived from Request Queue lengths, mean time between an I/O interrupt and the next Start I/O (SIO), percent time the unit is active, EXCP counts, or some other factor indicating the utilization of the device (or channel).

2. A Potential loading of the device (or channel) due to data sets which were allocated to the device (channel), but have not yet been OPENed and begun contributing to the Actual loading. This information is derived from the number of data sets allocated and the anticipated loading of each data set.

The Actual loading information must be kept for a series of time intervals. A series of time intervals is required, in order to obtain a short history of the activity on the device (channel) for time averaging purposes.

The method of keeping this information by time interval for the Actual loading on a device (channel) is envisioned as a shift register, where current activity is accumulated in a high-order portion of the register and the register is shifted right at the end of each time period. The following example is used to illustrate accumulation over four time periods:

(Image Omitted)

Actual loading information is accumulated into box A(1). After a period of time T(A), A(4) is shifted out, A(3) is shifted into A(4), A(2) into A(3), A(1) into A(2), and A(1) is reset to zero. Accumulation is then begun into A(1) for another period T(A). The value T(A) should be empirically determined, so that it will yield a relatively smooth...