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SubjectRe: [ANNOUNCE] high-res-timers patches for 2.6.6
Mark Gross wrote:
> On Friday 11 June 2004 15:33, George Anzinger wrote:
>>I have been thinking of a major rewrite which would leave this code alone,
>>but would introduce an additional list and, of course, overhead for
>>high-res timers. This will take some time and be sub optimal, so I wonder
>>if it is needed.
> What would your goal for the major rewrite be?
> Redesign the implementation?
> Clean up / re-factor the current design?
> Add features?

Mostly I would like to make it "clean" enough to get the community to accept it.
As I look at the current implemtation, the biggest intrusion into the "normal"
kernel is in the timer list area. Thus, my thinking is to introduce a second or
slave list which would only be used by HR timers. This list would be "checked"
by putting a "normal" i.e. add_timer, timer in place to mark the jiffie that a
HR timer was to expire in. The "check" code would then set up the HR interrupt
to expire the timer.

I am also considering removing a lot of the ifdefs one way or another. AND, I
think I can make the whole thing configureable at boot time just as the
pm/TSC/etc. timers are.
> I've been wondering lately if a significant restructuring of the
> implementation could be done. Something bottom's up that enabled changing /
> using different time bases without rebooting and coexisted nicely with HPET.
> Something along the lines of;
> * abstracting the time base's, calibration and computation of the next
> interrupt time into a polymorphic interface along with the implementation of
> a few of your time bases (ACPI, TSC) as a stand allown patch.

Uh, is this something like the current TSC/ pmtimer/ HPET/ PIT selection code in
the x86? Or do you have something else in mind here. Given the goal of
integration with and inclusion in the kernel, I don't want to wander
too far from what they are doing now.

> * implement yet another polymorphic interface for the interrupt source used by
> the patch, along with a few interrupt sources (PIT, APIC, HPET <-- new )
> * Implement a simple RTC-like charactor driver using the above for testing and
> integration.

I am not sure what wants to be done here. I have to keep in mind that x86 is
only one of many archs. I would like to keep it as simple as possible in this
area. See the include/linux/hrtime.h file for the arch interface we are now using.

> * Finally a patch to integrate the first 3 with the POSIX timers code.
> What do you think?
> --mgross
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George Anzinger
Preemption patch:

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