The reason I ask is that when looking at this comment from December 2014 , and doing some reading about what intel_powerclamp is doing , I think that it could be very beneficial for battery life to force the CPU into a higher c-state when idle. As of 5.4-current, MWAIT is going to C1 when idle in all cases , and I wish to know if that's changed since.
Re: any updates for apmd exposing c-state preferences?
On Tue, Mar 10, 2015 at 9:51 PM, Nicholas Sielicki <[hidden email]> wrote:
> I'm curious if there are any planned updates to apmd with regards to exposing a means for a user to set which c-state a processor should go into.
> As of 5.4-current, MWAIT is going to C1 when idle in all cases , and I wish to know if that's changed since.
Actually, that was disabled as it caused *increased* power consumption
on many boxes. There's work in progress to have the kernel used the
C-state information provided by ACPI so that it uses MWAIT properly
for the involved system, including the higher C-states. The main
hold-up is getting it to work robustly on various systems; sthen@ has
one box which hangs as soon as it goes multiuser with the in-progress
work. Once I figure out which rule I'm not following (or which rule
the _system_ isn't following and how to detect that...) there will be
a wider round of testing...