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

Robert Hancock
2007-12-08T03:51:53Z

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.

>
> 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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Robert Hancock Saskatoon, SK, Canada
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