notify userland about C-state changes
Andriy Gapon
avg at FreeBSD.org
Wed Oct 3 13:08:33 UTC 2012
on 02/10/2012 20:18 Sean Bruno said the following:
>
>> The following patch adds only per-CPU notifications.
>>
>> acpi_cpu: explicitly notify userland about c-state changes
>>
>> diff --git a/sys/dev/acpica/acpi_cpu.c b/sys/dev/acpica/acpi_cpu.c
>> index 82e204a..15201f9 100644
>> --- a/sys/dev/acpica/acpi_cpu.c
>> +++ b/sys/dev/acpica/acpi_cpu.c
>> @@ -1054,6 +1054,8 @@ acpi_cpu_notify(ACPI_HANDLE h, UINT32 notify, void *context)
>> ACPI_SERIAL_BEGIN(cpu);
>> acpi_cpu_set_cx_lowest(sc);
>> ACPI_SERIAL_END(cpu);
>> +
>> + acpi_UserNotify("PROCESSOR", sc->cpu_handle, notify);
>> }
>>
>> static int
>>
>
> So quick question, does this happen a lot on a system with a sporadic
> workload? Does this introduce overhead to the system to service the
> notification requests?
I am not sure who can answer this question. It is up to ACPI platform to decide
when it changes _available C-states_. OS doesn't have control over that.
P.S. I hope you haven't confused this notification for a notification about
_current_ C-state changing.
--
Andriy Gapon
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