Re: x86_64 dynticks not working prev: cpuidle, dynticks compatible or no?

[Ed Sweetman <safemode2@comcast.net>]

Robert Hancock wrote:
> Ed Sweetman wrote:
> > System is idle now, previously it was doing something i couldn't halt 
> > at the time.  I'm looking at "Local timer interrupts" in the "Loc:" 
> > section of /proc/interrupts.
> > Across 1 second while the system is pretty much idle, i still get 300 
> > interrupts. My HZ variable is set to 300 in the kernel config, so 
> > this is expected but I was under the assumption that 
> > dynticks/tickless being compiled in would cause that to be much lower.
> >
> > Am I reading the wrong section of /proc/interrupts  to verify if 
> > dynticks is working or not? Again, i see no difference in cpu temp at 
> > all.
>
> Try running powertop ( http://www.lesswatts.org/projects/powertop/ ) 
> and see what it reports.
>
> I don't think dynticks will generally save huge amounts of power on a 
> typical desktop machine. The big gains come from being able to stay in 
> deep sleep C-states (C2/C3) for longer periods of time, but most 
> desktop machines only enable sleep states down to C1.
I tried running powertop, it complains about not having timer 
statistics, I looked throughout the kernel config for a timer stat 
option, but can't find one.

I didn't have hpet compiled in, i'm not sure if this is required but a 
lot of places seem to suggest hpet and high precision timer and tickless 
be compiled together.  I also disabled cpuidle and i'll reboot and try 
that.



> > In case it helps, this is an athlon64 x2 with apic functioning and 
> > both cores active in 64bit mode. dmesg is below.
> > not related :
> > Some additional notes:  it87 is my lm_sensor, it doesn't work in this 
> > kernel, yet it did in 2.6.22.  Perhaps enabling high precision timers 
> > changed something in acpi land.
> >
> > I enabled tcp dma offloading in this kernel, i get debugging output 
> > related to it, error is at the last line.  No corruption or otherwise 
> > bad behavior.   Transferring via cifs at 9.7MB/sec "incoming" took 
> > about 15% of one cpu...  I never bothered to check if that is the 
> > norm but i suspect i'll be removing that feature as it seems to not 
> > play nice with the kernel.

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