Energy Efficient Implementation Of Read-Copy Update For Light Workloads Running On Systems With Many Processors
AssigneeInternational Business Machines Corporation
InventorPaul E. McKenney
Life of this patent
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Abstract
A technique for determining if a processor in a multiprocessor system implementing a read-copy update (RCU) subsystem may be placed in a low power state. The technique may include performing a first predictive query of the RCU subsystem to request permission for the processor to enter the low power state. If permission is denied, the processor is not placed in the low power state. If permission is granted, the processor is placed in the low power state for a non-fixed duration. Regardless whether permission is denied or granted, a second confirming query of the RCU subsystem is performed to redetermined whether it is permissible for the processor to be in the low power state.
Claims21
In a multiprocessor computer system having two or more processors operatively coupled to one or more memory devices and implementing a read-copy update (RCU) subsystem, a method for determining if a processor may be placed in a low power state, comprising:
- performing a first predictive query of said RCU subsystem to request permission for one of said processors to enter said low power state;
- if said permission is denied, refraining from placing said processor in said low power state;
- if said permission is granted, placing said processor in said low power state for a non-fixed duration;
- and
- regardless whether said permission is denied or granted, performing a second confirming query of said RCU subsystem to redetermine whether it is permissible for said processor to be in said low power state.
A multiprocessor system, comprising:
- two or more processors;
- a memory coupled to said processors, said memory including a computer useable medium tangibly embodying at least one program of instructions executable by said processors to implement a read-copy update (RCU) subsystem and to perform operations for determining if a processor may be placed in a low power state, said operations comprising:
- performing a first predictive query of said RCU subsystem to request permission for one of said processors to enter said low power state;
- if said permission is denied, refraining from placing said processor in said low power state;
- if said permission is granted, placing said processor in said low power state for a non-fixed duration;
- and
- regardless whether said permission is denied or granted, performing a second confirming query of said RCU subsystem to redetermine whether it is permissible for said processor to be in said low power state.
A computer program product, comprising:
- one or more machine-useable storage media;
- program instructions provided by said one or more media for programming a multiprocessor data processing platform to implement a read-copy update (RCU) subsystem and to perform operations for determining if a processor may be placed in a low power state, said operations comprising:
- performing a first predictive query of said RCU subsystem to request permission for one of said processors to enter said low power state;
- if said permission is denied, refraining from placing said processor in said low power state;
- if said permission is granted, placing said processor in said low power state for a non-fixed duration;
- and
- regardless whether said permission is denied or granted, performing a second confirming query of said RCU subsystem to redetermine whether it is permissible for said processor to be in said low power state.
The computer program product of claim 21, wherein said processor is determined to have no other work to perform if it is in an idle state with no pending scheduling change and no other immediate processing that needs to be performed by said processor.
Dependencies are inferred from the claim text.