RFC: setting performance_cx_lowest=C2 in -HEAD to avoid lock contention on many-CPU boxes

[Adrian Chadd]

On 25 April 2015 at 11:02, K. Macy <kmacy at freebsd.org> wrote:
> Um, don't you care more about power savings when it's on battery?

right, that's what I'm changing performance_cx_lowest, and not
economy_cx_lowest.

performance == AC power
economy == battery

> On Apr 25, 2015 10:44 AM, "Adrian Chadd" <adrian at freebsd.org> wrote:
>>
>> Oh the other thing, which I just mentioned to kip in IRC - all of the
>> intel laptops I've tested (and that's a long list) don't enter CPU C7
>> if the power is plugged in.
>>
>> Ie:
>>
>> * power in, ACPI C2 -> CPU C6
>> * power in, ACPI C3 - CPU C6
>> * battery - ACPI C2 -> CPU C6
>> * battery -> ACPI C3 -> CPU C7
>>
>> So having performance_cx_lowest=C3 is effectively a no-op on the
>> devices that it'd matter on, so it's okay to just flip it to C2.
>>
>>
>>
>> -adrian