On 09/02/09 11:08, Garrett D'Amore wrote: > Madhavan Venkataraman wrote: >> On 09/01/09 17:31, Garrett D'Amore wrote: >>> Joerg Schilling wrote: >>>> Jerry Gilliam <jerry.gilliam at sun.com> wrote: >>>> >>>> >>>>> 2. Project Summary >>>>> 2.1. Project Description: >>>>> The tickless project aims at implementing the services >>>>> provided by the >>>>> clock cyclic in an event driven fashion. The first >>>>> sub-project is the >>>>> decoupling of the lbolt and lbolt64 variables from >>>>> clock(). These two >>>>> variables are incremented at each firing of the clock >>>>> cyclic and provide >>>>> a time reference to the system. They are being replaced by >>>>> two routines >>>>> that are backed by gethrtime(), the existing >>>>> ddi_get_lbolt() and >>>>> the new ddi_get_lbolt64(), introduced as a migration path >>>>> for existing >>>>> non-DDI compliant consumers. >>>>> >>>> >>>> If this results in being able to sleep with less than 10 ms >>>> granularity without >>>> setting a high-res tick, you get many + from me! >>>> >>> >>> Actually, I could really use the ability to use a timer based >>> service that had a smaller window than 10 msec. For example, many >>> audio devices have crummy interrupt capabilities... its a lot nicer >>> (smoother audio) if I have a reliable way to get a periodic running >>> at smaller intervals. (5 to 10 msec, but with precision -- the >>> current stuff is simply too coarse.) >>> >>> This would simplify a lot of audio device drivers. And make them >>> more robust as well. :-) >>> >>> - Garrett >>> >> The callout subsystem has been redesigned to support small and high >> resolution >> timers. The condition variable module has also been enhanced to make >> use of the >> high resolution timers. (see functions that end with _hires in >> condvar.c). However, >> this is not exported via DDI. If some consolidation private driver >> wants to cheat >> and use these interfaces (ugh), it can. But if you feel there is a >> real need, someone >> should work to export the hires CV interfaces to DDI. What I am >> saying is that >> the functionality is there. It just needs to be exported. > > Can I use fine grained timers with ddi_periodic()? Or is it still > only tick granularity? Unfortunately not. It only supports 10 millisecond granularity even if hires_tick is set. The interface itself accepts hrtime_t. But internally, the interval is rounded up to the nearest 10 ms boundary. That whole interface needs to be revisited and its implementation revamped. A whole timer subsystem has been implemented there with many issues. But that is a separate topic.
Madhavan
