Date: Wed, 03 Oct 2012 16:08:30 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: sbruno@FreeBSD.org Cc: "freebsd-acpi@freebsd.org" <freebsd-acpi@FreeBSD.org>, Sean Bruno <seanbru@yahoo-inc.com> Subject: Re: notify userland about C-state changes Message-ID: <506C38CE.4090400@FreeBSD.org> In-Reply-To: <1349198313.4246.3.camel@powernoodle.corp.yahoo.com> References: <504EDBEB.6010104@FreeBSD.org> <1349198313.4246.3.camel@powernoodle.corp.yahoo.com>
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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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