Template Version: @(#)sac_nextcase 1.64 07/13/07 SMI
This information is Copyright 2007 Sun Microsystems
1. Introduction
1.1. Project/Component Working Name:
CPUFreq HAL
1.2. Name of Document Author/Supplier:
Author: Anup Pemmaiah
1.3 Date of This Document:
05 December, 2007
4. Technical Description
4.0 Introduction
===============
This project delivers the CPU power management related support
for the HAL interfaces used by the GNOME Power Manager (GPM)
desktop application to control CPU power management behavior.
4.1 Background and Summary
=========================
LSARC/2006/462 proposed adding GNOME Power Manager (GPM), a
workstation power management GUI, to the Solaris GNOME desktop.
One of the components provided by GPM is a preference dialog used
to configure CPU power management settings. In order to support
the CPU power management dialog, the host OS (Solaris) is required
to provide backend support for the pre-defined Hardware Abstraction
Layer (HAL) interfaces [1]. See PSARC/2005/399 for more information
on HAL.
HAL defines a CPU Freq interface that it uses to support CPU power
management. This case, defines those interfaces and explains what
existing Solaris interfaces will be used to support the HAL CPU Freq
interface.
4.2 Block Diagram
=================
An end-to-end GNOME CPU power management system diagram.
The dotted lines indicate the boundaries of the pieces
implemented by this project.
+--------------------------+
| |
|GNOME CPU power management| LSARC/2006/462 GNOME-2.16
| applet GUI |
+--------------------------+
^
| (D-bus)
| JDS consolidation (up)
-------------+--------------------------------------------------
| ON consolidation (below)
| (D-bus)
v
+-------------------------+
| HAL daemon (hald) | PSARC/2005/399 Tamarack
...............................
: | | :
: +--------------------+ | :
: | CPU Freq | | :
: | daemon | | : +-----------+
: | hald-addon-cpufreq | |<---->| kstat(1M) |
: +--------------------+----+ : +-----------+
: ^ : ^
:.........|...................: |
| |
| |
v |
+-------------------------+ |
| power.conf | |
| | |
| pmconfig utility | |
+-------------------------+ |
^ |
| |
| (ioctl) | USER
-----------+------------------------------+---------------
| | KERNEL
| |
v |
+------------------+ |
| | | (kstat)
| cpu driver |<------------------+
| |
+------------------+
4.3 Project Details
==================
4.3.1 Data flow of CPU Freq HAL method interface
----------------------------------------------
GPM uses the HAL CPU Freq Interface to manage CPU power management
policies on the host workstation. The Interface has one major CPU power
management concept of interest to this case. HAL refers to CPU power
management policy types as governors. The two governors that this case
intends to support initially are the "On Demand" governor and the
"Performance" governor.
The "On Demand" governor is a CPU power management policy whereby
dynamic CPU frequency scaling is performed by monitoring CPU utilization
and scaling the frequency when appropriate.
The "Performance" governor is a CPU power management policy intended
to allow the desktop to get full CPU utilization all the time (i.e.,
no frequency scaling).
Both governors will be implemented using the power.conf(4) cpupm keyword
introduced by PSARC/2005/067. "On Demand" translates to cpupm being
enabled and "Performance" translates to cpupm being disabled.
Also of interest to this case, is that the CPU Freq interface supports
defining a performance property for governors. The performance property
is meant to provide the governor with a hint at how aggressively it should
manage CPU power. This case proposes to use the frequency performance
attribute as a means of calculating a cpu-threshold value for
power.conf(4). The cpu-threshold keyword was introduced by PSARC/2005/067.
4.3.2 Interfaces
--------------
Interfaces Exported:
All the interfaces exported by this project are HAL
cpu-freq related and detailed information can be found
on the HAL webpage [1]. They are "Committed" level.
These interfaces can be used by GPM.
Interface
Method Name Return Parameters Comments
-------------------------------------------------------------------
SetCPUFreqGovernor void string Type of governor (policy)
to set as described in 3.1.
GetCPUFreqGovernor string None Returns current policy
GetCPUFreqAvailable string[] None Returns the list of
Governors supported policies
SetCPUFreqPerformance void int Set the performance of the
(between 1-100) CPU Freq scaling. Higher
the value is better perfo-
rmance. In our implementa-
tion, this value is used
to set the CPU Freq
scaling by varying the
"cpu-threshold" parameter
in the power.conf.
GetCPUFreqPerformance int None Return the current
performance value set by
SetCPUFreqPerformance
SetCPUFreqConsiderNice void Bool Whether or not niced processes
(consider should be considered on CPU
niced load calculation.
processes) Note: Since none of the current
CPU power management policies
consider niced processes this
method just returns
CPUFreq.NoSuitableGovernor)
GetCPUFreqConsiderNice bool None Whether nice'ed processes
are considered by the governor.
Note: Since none of the current
CPU power management policies
consider niced processes this
method just returns
CPUFreq.NoSuitableGovernor)
The processor specific properties interface
Interface Type Comments
---------------------------------------------------------------
processor.number int The internal processor number
processor.throttle boolean Whether the processor supports
throttling to decrease it's own
clock speed
processor.maximum_speed long The maximum speed of the processor
in units of MHz
Interfaces Imported:
Interface Comments
---------------------------------------------------------------
power.conf(4) Used by SetCPUFreqGovernor & SetCPUPerformance to
edit the "cpupm" & "cpu-threshold" parameters in
power.conf respectively. The other method
interfaces reads these values and return the
current values that are set
pmconfig(1M) When power.conf is edited anytime, pmconfig should
be called for the edited power.conf to take effect
cpu_info kstat Used by HAL cpu freq interface to get the max
"clock_MHz" supported freq
cpu_info kstat To check if processor supports power management
"supported_frequencies_Hz"
FOOTNOTES:
==========
[1] More info about HAL interface can be found at
http://people.freedesktop.org/~david/hal-spec/hal-spec.html
6. Resources and Schedule
6.4. Steering Committee requested information
6.4.1. Consolidation C-team Name:
ON
6.5. ARC review type: FastTrack
6.6. ARC Exposure: open
