Hi all,

Attached is the dynamic tick patch for x86 to play with
as I promised in few threads earlier on this list.[1][2]

The dynamic tick patch does following:

- Separates timer interrupts from updating system time

- Allows updating time from other interrupts in addition
  to timer interrupt

- Makes timer tick dynamic

- Allows power management modules to take advantage of the
  idle time inbetween skipped ticks

- Might help with the whistling caps?

The patch should be non-intrusive where possible. The system
boots with the regular timers, and then later on switches on
the dynamic tick if the selected driver implements get_hw_time()
function.

Currently supported timers are TSC and ACPI PM timer. Other
timers should be easy to add. Both TSC and ACPI PM timer
rely on the PIT timer for interrupts, so the maximum skip
inbetween ticks is only few seconds at most.

Please note that this patch alone does not help much with
power savings. More work is needed in that area to make the
system take advantage of the idle time inbetween the skipped
ticks.

The patch is based on a similar patch for ARM OMAP. The history
of the dynamic tick patch is something like:

Orignal 2.4 VST patch by George Anzinger -->
2.6 OS/390 next_timer_interrupt() patch Martin Schwidefsky --> 
2.6 OMAP dynamic tick patch --> This patch

As this patch is related to the VST/High-Res timers, there
are probably various things that can be merged. I have not
yet looked at what all could be merged.

I'd appreciate some comments and testing!

Regards,

Tony

[1] http://lkml.org/lkml/2004/12/11/24
[2] http://lkml.org/lkml/2005/1/13/104