On Friday, September 07, 2012, Daniel Lezcano wrote:
Since commit 46bcfad7a819bd17ac4e831b04405152d59784ab, cpuidle: Single/Global registration of idle states
we have a single registration for the cpuidle states which makes sense. But now two new architectures are coming: tegra3 and big.LITTLE.
These architectures have different cpus with different caracteristics for power saving. High load => powerfull processors, idle => small processors.
That implies different cpu latencies.
This patchset keeps the current behavior as introduced by Deepthi without breaking the drivers and add the possibility to specify a per cpu states.
- Tested on intel core 2 duo T9500
- Tested on vexpress by Lorenzo Pieralsi
- Tested on tegra3 by Peter De Schrijver
Daniel Lezcano (6): acpi : move the acpi_idle_driver variable declaration acpi : move cpuidle_device field out of the acpi_processor_power structure acpi : remove pointless cpuidle device state_count init
I've posted comments about patches [1-3/6] already. In short, I don't like [1/6], [2/6] would require some more work IMO and I'm not sure about the validity of the observation that [3/6] is based on.
Yes, I agree that the ACPI processor driver as a whole might be cleaner and it probably would be good to spend some time on cleaning it up, but not necessarily in a hurry.
Unfortunately, I also don't agree with the approach used by the remaining patches, which is to try to use a separate array of states for each individual CPU core. This way we end up with quite some duplicated data if the CPU cores in question actually happen to be identical.
What about using a separate cpuidle driver for every kind of different CPUs in the system (e.g. one driver for "big" CPUs and the other for "little" ones)?
Have you considered this approach already?
cpuidle : add a pointer for cpuidle_state in the cpuidle_device cpuidle : use per cpuidle device cpu states cpuidle : add cpuidle_register_states function
drivers/acpi/processor_driver.c | 2 +- drivers/acpi/processor_idle.c | 27 +++++++++++++++------- drivers/cpuidle/cpuidle.c | 42 ++++++++++++++++++++++++++++------- drivers/cpuidle/governors/ladder.c | 22 +++++++++--------- drivers/cpuidle/governors/menu.c | 8 +++--- drivers/cpuidle/sysfs.c | 3 +- include/acpi/processor.h | 3 -- include/linux/cpuidle.h | 11 ++++++-- 8 files changed, 76 insertions(+), 42 deletions(-)
Thanks, Rafael