[RFC PATCH V1 0/2] cpuidle: global registration of idle states withper-cpu statistics
From: Trinabh Gupta
Date: Tue Mar 22 2011 - 08:47:59 EST
This patch series is an early RFC to discuss the feasibility of
avoiding registering of idle states from each cpu.
The core change is to split the cpuidle_device structure into parts
that can be global and parts that has to remain per-cpu. The per-cpu
pieces are mostly generic statistics that can be independent of
current running driver.
Motivation:
* Simplify the cpuidle subsystem framework and have
registration/unregistration done by single cpu.
* Minimise the data structure that needs to be maintained for multiple
cpuidle drivers
* Reference: https://lkml.org/lkml/2011/2/10/37
Advantages:
* Make the cpuidle framework simple for most use cases where C-States
are symmetric. In case there are asymmetric C-States detected,
fallback mechanism should be incorporated to maintain the system
functional
https://lkml.org/lkml/2011/2/10/257
https://lkml.org/lkml/2011/2/10/37
* Non x86 archs that does not have asymmetric C-States like POWER, may
not need the fallback mechanism and hence the framework will be
simple for most use cases.
Disadvantages:
* Asymmetric C-States are part of x86 ACPI specification. Incorrect
handling may functionally affect the system
* Incorporating per-cpu masks for each state to allow/dis-allow global
states on subset of CPUs may result in an implementation that is
not better than current solution of having per-cpu states.
This patch series applies on top of the pm_idle cleanup patch
https://lkml.org/lkml/2011/3/22/150 (cpuidle: Cleanup pm_idle and
include driver/cpuidle.c in-kernel)
This patch series is tested on x86 Nehalem system with multiple ACPI
C-States.
This patch series has limitations of not handling multiple driver
registration and switching between drivers on all CPUs mainly due to
incomplete handling of per-cpu enable/disable and driver_data.
Please let us know your comments and suggest possible approaches to
the problem.
---
Trinabh Gupta (2):
cpuidle: API changes in callers using new cpuidle_state_stats
cpuidle: Data structure changes for global cpuidle device
drivers/acpi/processor_driver.c | 19 +---
drivers/acpi/processor_idle.c | 45 ++++++----
drivers/cpuidle/cpuidle.c | 169 ++++++++++++++++++++++--------------
drivers/cpuidle/cpuidle.h | 4 -
drivers/cpuidle/driver.c | 24 -----
drivers/cpuidle/governor.c | 10 +-
drivers/cpuidle/governors/Makefile | 2
drivers/cpuidle/governors/menu.c | 16 ++-
drivers/cpuidle/sysfs.c | 62 +++++++------
drivers/idle/default_driver.c | 39 +++-----
include/linux/cpuidle.h | 70 ++++++++++-----
11 files changed, 245 insertions(+), 215 deletions(-)
--
-Trinabh
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