Event timers

John Baldwin jhb at freebsd.org
Tue May 25 12:49:39 UTC 2010

On Monday 24 May 2010 11:57:39 am Alexander Motin wrote:
> Hi.
> You should agree that event timers code we have now (hardclock,
> statclock and profclock source) is real mess. The code is completely
> machine-dependent, many times duplicated (I have found 4 or 5 equal
> implementations and many more trivial ones), very tangled and
> inflexible. While it is acceptable for some platforms with single
> interrupt source running on hz, x86 with it's many different timers
> definitely doesn't look good. So I've decided to clean it.
> I have defined several points on that way:
> 1*. clean low-level timer drivers from unrelated stuff,
> 2*. make some common code machine-independent,
> 3. write common driver API for event timers (alike to one we have now
> for time counters) to make adding more drivers possible,
> 4. add support for HPET as event timer in addition to time counter,
> 5. add support for timers in one-shot mode (LAPIC and HPET).

Have you looked at the dynamic ticks patches on hackers@?  Those already 
include changes for 5), although he currently only has support for LAPIC and 
is working on adding HPET support.

John Baldwin

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