Processor Idle Synchronization for Power Management
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Solution Overview
Problem
Modern computing systems face inefficiencies in power management at fine levels of granularity, leading to lost power-saving opportunities due to the lack of synchronization between system devices and the system processor's idleness based on operating system schedules.
Innovation Solution
Implementing a power management logic that synchronizes the idleness of system devices with the operating system schedule, using a timer to transition devices between active and idle states, and selectively powering devices during active and idle windows to achieve aggressive power savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If drivers emulate hardware timers to turn off devices after predetermined idle time, then power consumption is reduced at coarse granularity levels, but power-saving opportunities are lost at fine granularity levels due to lack of synchronization with processor idle states
Solution Approach 1:
The patent merges the idle detection mechanisms of the processor and system devices by having devices synchronize their idle states with the processor's OS idle events. Instead of independent timer-based idle detection, devices now align their power management with the centralized OS idle schedule, combining previously separate idle management functions into a unified system-wide approach.
Solution Approach 2:
The patent implements a feedback mechanism where system devices receive notifications about processor idle events and adjust their own idle states accordingly. The OS generates idle events that propagate to devices, creating a feedback loop that enables coordinated power management across the system based on actual processor workload conditions rather than predetermined timers.
2Ease of operation
If devices operate independently with predetermined idle timers, then device control is simplified, but synchronization with processor idle states is lost leading to suboptimal power management
Solution Approach 1:
The patent makes the OS idle event mechanism universal by having it serve both the processor and all system devices simultaneously. The same idle event that puts the processor to sleep also triggers devices to enter idle states, eliminating the need for separate predetermined timers in each device while maintaining simple control through a unified event-driven approach.
3Reliability
If system devices remain active during processor idle periods, then device responsiveness is maintained, but power consumption increases without achieving system-wide power savings
Solution Approach 1:
The patent applies preliminary action by having devices enter idle states in advance when the OS generates an idle event, before the processor actually enters its idle state. This preliminary synchronization ensures devices are ready to be inactive when the processor is idle, while still allowing quick wake-up through interrupt mechanisms if needed, thus maintaining responsiveness while capturing power savings.
Data Source
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AI summary
Systems and methods of power management provide for controlling the idleness of a processor based on an operating system schedule. The idleness of at least one device is synchronized with the idleness of the processor. Idleness synchronization may involve deferring bus transactions, suspending memory refresh, turning off power to clock sources and turning off power to combinatorial logic during an idle window in the OS schedule.