1kHz noise from C3 sleep

[Nate Lawson]

Alexander Leidinger wrote:
> On Thu, 20 Oct 2005 11:25:59 -0700
> Nate Lawson <nate at root.org> wrote:
> 
> 
>>Alexander Leidinger wrote:
>>
>>>Nate Lawson <nate at root.org> wrote:
>>>
>>>[Moving to -current]
>>>
>>>
>>>>>I wonder if moving to HZ=1000 on amd64 and i386 was really all that good
>>>>>of an idea.  Having preemption in the kernel means that ithreads can run
>>>>>right away instead of having to wait for a tick, and various fixes to
>>>>>4BSD in the past year have eliminated bugs that would make the CPU wait
>>>>>for up to a tick to schedule a thread.  So all we're getting now is a
>>>>>10x increase in scheduler overhead, including reading the timecounters.
>>>>
>>>>
>>>>I use hz=100 on my systems due to the 1 khz noise from C3 sleep. 
>>>>Windows has the same problem.
>>>
>>>
>>>My laptop makes noises when being (more or less) idle (I think I enabled
>>>C3...). Does this mean I should try to change HZ?
>>
>>Sure, you can do it from a tunable (kern.hz I think), you don't have to 
>>recompile.
> 
> 
> No, a HZ of 100 doesn't work, the laptop still makes noises. And it
> only has C2, no C3...


Change to C1 (which is just HLT).  If it still makes noise, it's not 
your C2 or C3 sleep.

-- 
Nate