System interconnect dynamic scaling by lane width and operating frequency balancing

• US 9,524,013 B2
• Filed: 04/16/2014
• Issued: 12/20/2016
• Est. Priority Date: 04/16/2014
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Dreps, Daniel Mark, Ferraiolo, Frank D., Haridass, Anand, Jayaraman, Prasanna
• Primary Examiner(s): Rahman, Fahmida
• Application Number:
  US14/253,916
• Publication Number:
  US 20150301575A1
• Time in Patent Office: 979 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 1/324 by lowering clock frequency
• CPC Class Codes: G06F 1/3243 Power saving in microcontroller unit
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

Interface management techniques provide reduced power consumption along with reducing heat and EMI generation in a computer system having multiple interconnected processing units. Physical link layers of external interfaces that interconnect the processing units have dynamically adjustable bandwidth provided by an adjustable width and adjustable operating frequency. The bandwidths may be dynamically adjusted by predicting interface bandwidth requirements. From a required bandwidth, an active width and an operating frequency for the physical link layers are determined and set. The interface is operated according to the determined width and operating frequency.

Claims

1. A controller for controlling a dynamically adjustable bandwidth of a physical link layer of an external interface for interconnecting processing units of a computer system, the controller comprising:

an interface for receiving an indication of a required bandwidth for operation of the physical link layer; and

a control circuit that, from the required bandwidth, determines an active width and operating frequency for the physical link layer that meet the required bandwidth, sets a current active width of the physical link layer to the determined active width, sets a current operating frequency of the physical link layer to the determined operating frequency, whereby the physical link layer is operated using the current active width and the current operating frequency, wherein the control circuit predicts a future bandwidth requirement for the physical link layer, wherein the interface receives the predicted future bandwidth requirement, wherein the control circuit further determines the active width and operating frequency for the physical link layer by determining whether or not a current utilization of the external interface is less than a threshold usage, evaluates a quality of the predicting, and compares the quality of the predicting to a threshold quality, and wherein the control circuit sets at least one of the current operating frequency or the current active width responsive to determining that the current utilization of the external interface is less than the threshold usage and responsive to determining that the quality of the predicting is less than the threshold quality by reducing the at least one of the current operating frequency or the current active width, wherein the control circuit sets the current operating frequency responsive to determining that the current utilization of the external interface is less than the threshold usage and responsive to determining that the quality of the predicting is less than the threshold quality by reducing the current operating frequency while maintaining the current active width of the physical link layer.

2. The controller of claim 1, wherein the control circuit sets a current active width by, responsive to determining that the current utilization of the external interface is less than the threshold usage and responsive to the comparing determining that the quality of the predicting is greater than the threshold quality, reducing the current active width while the setting the current active operating frequency maintains the current operating frequency of the physical link layer.

3. The controller of claim 2, wherein the control circuit sets the current active width periodically by reducing the current active width to zero by powering down the physical link layer of the external interface at periodic intervals and re-powering the physical link layer of the external interface at the end of the periodic intervals.

4. The controller of claim 2, wherein the control circuit sets a current active width by, responsive to determining that the current utilization of the external interface is greater than the threshold usage, setting the current active width to a maximum width, and wherein the setting the current active operating frequency sets the current operating frequency of the physical link layer in conformity with the predicted future bandwidth requirement.

5. The controller of claim 4, wherein the control circuit predicts a shape of a predicted utilization of the external interface and controls the current active operating frequency in conformity with the shape of the predicted utilization.

6. A controller for controlling a dynamically adjustable bandwidth of a physical link layer of an external interface for interconnecting processing units of a computer system, the controller comprising:

an interface for receiving an indication of a required bandwidth for operation of the physical link layer; and

a control circuit that, from the required bandwidth, determines an active width and operating frequency for the physical link layer that meet the required bandwidth, sets a current active width of the physical link layer to the determined active width, sets a current operating frequency of the physical link layer to the determined operating frequency, whereby the physical link layer is operated using the current active width and the current operating frequency, wherein the control circuit predicts a future bandwidth requirement for the physical link layer, wherein the interface receives the predicted future bandwidth requirement, wherein the control circuit further determines the active width and operating frequency for the physical link layer by determining whether or not a current utilization of the external interface is less than a threshold usage, evaluates a quality of the predicting, and compares the quality of the predicting to a threshold quality, and wherein the control circuit sets at least one of the current operating frequency or the current active width responsive to determining that the current utilization of the external interface is less than the threshold usage and responsive to determining that the quality of the predicting is less than the threshold quality by reducing the at least one of the current operating frequency or the current active width, wherein the control circuit sets the current active width by, responsive to determining that the current utilization of the external interface is less than the threshold usage and responsive to determining that the quality of the predicting is greater than the threshold quality, reducing the current active width while maintaining the current operating frequency of the physical link layer.

7. A computer program product comprising a non-transitory computer-readable memory storing program instructions for execution by a computer system comprising a plurality of processing units coupled by external interfaces, the program instructions comprising program instructions for:

receiving an indication of a required bandwidth for operation of a physical link layer of a first one of the external interfaces;

from the required bandwidth, determining an active width and operating frequency for the physical link layer that meet the required bandwidth;

setting a current active width of the physical link layer to the determined active width;

setting a current operating frequency of the physical link layer to the determined operating frequency;

operating the physical link layer using the current active width and the current operating frequency;

predicting a future bandwidth requirement for the physical link layer;

receiving the predicted future bandwidth requirement;

determining whether or not a current utilization of the first one of the external interfaces is less than a threshold usage;

evaluating a quality of the predicting;

comparing the quality of the predicting to a threshold quality; and

setting at least one of the current operating frequency or the current active width responsive to determining that the current utilization of the first one of the external interfaces is less than the threshold usage and responsive to the comparing determining that the quality of the predicting is less than the threshold quality by reducing the at least one of the current operating frequency or the current active width, wherein the program instructions for setting at least one of the current operating frequency or the current active width reduce the current operating frequency while maintaining the current active width of the physical link layer.

8. A computer program product comprising a non-transitory computer-readable memory storing program instructions for execution by a computer system comprising a plurality of processing units coupled by external interfaces, the program instructions comprising program instructions for:

receiving an indication of a required bandwidth for operation of a physical link layer of a first one of the external interfaces;

from the required bandwidth, determining an active width and operating frequency for the physical link layer that meet the required bandwidth;

setting a current active width of the physical link layer to the determined active width;

setting a current operating frequency of the physical link layer to the determined operating frequency;

operating the physical link layer using the current active width and the current operating frequency;

predicting a future bandwidth requirement for the physical link layer;

receiving the predicted future bandwidth requirement;

determining whether or not a current utilization of the first one of the external interfaces is less than a threshold usage;

evaluating a quality of the predicting;

comparing the quality of the predicting to a threshold quality; and

setting at least one of the current operating frequency or the current active width responsive to determining that the current utilization of the first one of the external interfaces is less than the threshold usage and responsive to the comparing determining that the quality of the predicting is less than the threshold quality by reducing the at least one of the current operating frequency or the current active width, wherein the program instructions for setting at least one of the current operating frequency or the current active width reduce the current active width while maintaining the current operating frequency of the physical link layer.