Messages in this thread |  | | | From | Trinabh Gupta <> | | Subject | [RFC PATCH V1 0/2] cpuidle: global registration of idle states with per-cpu statistics | | Date | Tue, 22 Mar 2011 18:17:45 +0530 |
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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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