METHOD OF AND APPARATUS FOR DYNAMIC GRAPHICS POWER GATING FOR BATTERY LIFE OPTIMIZATION

• US 20120169747A1
• Filed: 12/28/2011
• Published: 07/05/2012
• Est. Priority Date: 12/28/2011
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Samson, Eric C., KABURLASOS, Nikos
• Granted Patent: US 8,806,243 B2
• Time in Patent Office: Days
• US Class Current: 345/522
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 9/5044 considering hardware capabilities
• CPC Class Codes: G06T 1/20 Processor architectures; Processor configuration, e.g. pipelining

Abstract

A method includes executing a workload on a graphics (GFX) core in a first mode the GFX core comprising a plurality of Subslices wherein each of the plurality of Subslices dissipates power. The method further includes calculating a number of clock cycles, Tfirst mode, required for the GFX core to perform the workload in the first mode during a first decision window comprising a plurality of clock cycles and calculating a number of clock cycles, Tsecond mode, required for the GFX core to perform the workload in a second mode during the first decision window wherein the second mode comprises executing the workload with fewer of the plurality of Subslices receiving power than when executing the workload in the first mode. It is then determined, based in part upon Tfirst mode and Tsecond mode, if an energy savings is possible by transitioning the GFX core to the second mode.

Claims

1. A method comprising:

executing a workload on a graphics (GFX) core in a first mode the GFX core comprising a plurality of Subslices wherein each of the plurality of Subslices receives power;

calculating a number of clock cycles, Tfirst mode, required for the GFX core to perform the workload in the first mode during a first decision window comprising a plurality of clock cycles;

calculating a number of clock cycles, Tsecond mode, required for the GFX core to perform the workload in a second mode during the first decision window wherein the second mode comprises executing the workload with fewer of the plurality of Subslices receiving power than when executing the workload in the first mode;

determining if the GFX core operated in a power down state during the first decision window;

determining, based in part upon Tfirst mode and Tsecond mode, if an energy savings is possible by transitioning the GFX core to the second mode if it is determined that the GFX core operated in a power down state during the first decision window; and

transitioning the GFX core to the second mode if it is determined that an energy savings is possible by transitioning the GFX core to the second mode.

2. The method of claim 1 further wherein determining if an energy savings is possible comprises:

evaluating;

Lkgsecond mode*Tfirst mode+(Lkgsecond mode+Lkgrest)*(Tfirst mode−

Tsecond mode)+fvmin*Vmin2*(Cfirst mode*Tfirst mode−

Csecond mode*Tsecond mode)

where Lkgsecond mode is a power leakage of the one or more Subslices receiving power in the second mode, Lkgrest is a power leakage of the GFX core exlusive of the power consumed by the plurality of Subslices, fvmin is the operating frequency of the GFX core, Vmin is the operating voltage of the GFX core, Cfirst mode is the switching capacitance of the GFX core executing in the first mode, and Csecond mode is the switching capacitance of the GFX core executing in the second mode; and

determining that the energy savings is possible if a result of the evaluation is a positive quantity.

3. The method of claim 2 further comprising estimating a value of Csecond mode.

4. The method of claim 3 wherein estimating the value of Csecond mode comprises estimating the value of Csecond mode utilizing post-silicon characterization.

5. The method of claim 1 wherein the power down state is an RC6 state.

6. An article of manufacture comprising:

a computer readable medium having stored thereon instructions which, when executed by a processor, cause the processor to;

execute a workload on a graphics (GFX) core in a first mode the GFX core comprising a plurality of Subslices wherein each of the plurality of Subslices receives power;

calculate a number of clock cycles, Tfirst mode, required for the GFX core to perform the workload in the first mode during a first decision window comprising a plurality of clock cycles;

calculate a number of clock cycles, Tsecond mode, required for the GFX core to perform the workload in a second mode during the first decision window wherein the second mode comprises executing the workload with fewer of the plurality of Subslices receiving power than when executing the workload in the first mode;

determine if the GFX core operated in a power down state during the first decision window;

determine, based in part upon Tfirst mode and Tsecond mode, if an energy savings is possible by transitioning the GFX core to the second mode if it is determined that the GFX core operated in a power down state during the first decision window; and

transition the GFX core to the second mode if it is determined that an energy savings is possible by transitioning the GFX core to the second mode.

7. The article of claim 6 wherein the instructions further cause the processor to determine if an energy savings is possible by evaluating:

Lkgsecond mode*Tfirst mode+(Lkgsecond mode+Lkgrest)*(Tfirst mode−

Tsecond mode)+fvmin*Vmin2*(Cfirst mode*Tfirst mode−

Csecond mode*Tsecond mode)

where Lkgsecond mode is a power leakage of the one or more Subslices receiving power in the second mode, Lkgrest is a power leakage of the GFX core exlusive of the power consumed by the plurality of Subslices, fvmin is the operating frequency of the GFX core, Vmin is the operating voltage of the GFX core, Cfirst mode is the switching capacitance of the GFX core executing in the first mode, and Csecond mode is the switching capacitance of the GFX core executing in the second mode; and

determining that the energy savings is possible if a result of the evaluation is a positive quantity.

8. The article of claim 7 wherein the instructions further cause the processor to estimate a value of Csecond mode.

9. The article of claim 8 wherein the instructions further cause the processor to estimate the value of Csecond mode utilizing post-silicon characterization.

10. The article of claim 10 wherein the power down state is an RC6 state.

11. A method comprising:

executing a workload on a graphics (GFX) core in a first mode the GFX core comprising a plurality of Subslices wherein not each of the plurality of Subslices receives power;

calculating a percentage of time that the GFX core operated in a power down state during a first decision window comprising a plurality of clock cycles;

determining if the percentage exceeds a predefined threshold;

determining, if the percentage exceeds a predefined threshold, if the percentage of time that the GFX core operated in the power down state during the first decision window is attributable to a periodic activity pattern; and

transitioning the GFX core to a second mode wherein the second mode comprises executing with more of the plurality of Subslices receiving power than when executing the workload in the first mode if it is determined that at least a portion of the percentage of time that the GFX core operated in the power down state during the first decision window is not attributable to the periodic activity pattern.

12. The method of claim 11 further comprising observing the operation of the GFX core during a plurality of decision windows to determine the periodic activity pattern.

13. The method of claim 11 wherein the power down state is an RC6 state.