Evaluation of Advanced Power Management for ClassCloud based on DRBL Rider Grid Technology Division National Center for High-Performance Computing Research Report

Outline Power Management APM / ACPI CPUFREQD Paper Concept Discussion

Power budget

Power Management Power management goals –Shut down unused devices selectively –Define a maximum period of inactivity –Shut down the entire system during longer periods of inactivity –Ready to restart if triggered by a wake-up event –Sensitive to potential hazards like shutting down the hard drive in the middle of a write operation –Keep the system cost about the same

System Management Mode System Management Mode (SMM) –Set of features that enables the CPU to slow down or stop its clock without deleting information –Stops the CPU and all of the peripherals –Requires a specialized BIOS and OS –To further power management capabilities, Intel introduced Advanced Power Management (APM) in 1992 Advanced Configuration and Power Interface (ACPI) in 1996

6 APM and ACPI APM –Shuts off power to peripheral components as needed –Configured in BIOS Advanced Configuration and Power Interface (ACPI) –Configures peripheral’s power setting from OS –Monitor CPU temperature and battery power –Standby mode and sleep mode Linux ACPI Client: Utility used to view ACPI settings

Requirements for APM/ACPI APM and ACPI require the following in order to function properly –An SMM-capable CPU –APM-compliant BIOS –Devices that will accept being shut off (“Energy Star”) –A system OS that knows how to request the shutdown of a particular device

Operating System Power Management (OSPM) Supported by Microsoft’s desktop operating systems via APM –OS/BIOS co-operation –When OS goes to idle condition it performs an access to a register that causes an SMI# –SMI handler puts system into low power state –APM required OS to trust the system BIOS

Current OSPM - ACPI Advanced Configuration and Power Management Interface (ACPI) –OS visible (SCI-based) as opposed to OS invisible (SMI-based) –OS/drivers/BIOS are in sync regarding power states Standard way for the system to describe its device config. & power control h/w interface to the OS –register interface for common functions system control events, processor power and clock control, thermal management, and resume handling Info on devices, resources, & control mechanisms Thermal Management

ACPI Advanced Configuration and Power Interface –Conceived by Intel, Microsoft, and Toshiba (the promoters) An “interface” specification –ACPI/OSPM replaces APM, MPS, and PnP BIOS Spec Allow OS-directed Power Management (OSPM) Defines –Hardware registers - implemented in chipset silicon –BIOS interfaces Configuration tables Interpreted executable function interface (Control Methods) Motherboard device enumeration and configuration –System and device power states –ACPI Thermal Model

11 Configure Advanced Power Management and the ACPI Tool The hardware information and configuration tool (ACPI) is available on most computers On many types of HW, the CPU frequency can be adapted to the load, which helps save battery time –Power management technologies require suitable HW and BIOS routines Level of APM and ACPI support depends on HW

12 Configure Advanced Power Management and the ACPI Tool (cont) In this objective, the following topics are described: –Power Saving Functions –APM –ACPI –powersave

13 What ACPI Offers ? Standardization industry-wide (Vendors to support ACPI in products instead of building their own power mgt) System and device power states Thermal model –Thermal zones, indicators, cooling methods BIOS interfaces –Motherboard configuration tables –Interpreted control methods Plug-and-play Complexity moved into OS

14 What ACPI Offers (cont) ? System –Mechanisms for putting computer as a whole in sleep/wake states Devices –ACPI tables describe motherboard devices Power states Controls for managing states Processor –Detecting idle state and swapping to low power Batteries –Querying and controlling battery behavior

15 Power Saving Functions Systems offer (some of) the following functions: –Standby –Suspend to memory (STM) : S3 –Hibernation (Suspend to disk – STD) :S4 –Battery monitor –Automatic power-off –Shutdown of system components –Processor speed control Processor speed levels available are: –Performance –Powersave –Dynamic

ACPI Software Components ACPI Subsystem –ACPI Tables / BIOS / registers – 3 components –Interacts with ACPI Hardware Policy Manager (OSPM) –Sets and Monitors System Policies –User Interface Allows User Input to Policy Device Drivers –EC, SMBus, Smart Battery

ACPI Global States and Transitions

ACPI Processor Power States Latency C1 < C2 < C3 Power C1 > C2 > C3 Power Throttling

Summary of functional areas covered by ACPI System Power Management Device Power Management Processor power management Device and processor performance management

ACPI functionalities (cont.) Plug and Play System Events Battery management Thermal management A standard hw and sw interface between OS and Embedded Controller

Cpufreqd Small daemon –CPU speed adjustment –CPU voltage adjustment ACPI support Device –Fans –Thermal controller through ACPI –FSB –NVIDIA graphic card

Paper Concept Experiment Case –PXE boot with HD –PXE boot without HD App Case –FFmpeg (video encoder) –mencoder (video encoder) –WavPack (audio encoder) Running on different governors Find the critical point in each case DRBL cpufreqd module

????? Great! Discussion ?