Paul Davis wrote: > I hope this is not true: > > "Embedded systems often need to poll hardware or do other tasks on a > fixed schedule. POSIX timers make it easy to arrange any task to get > scheduled periodically. The clock that the timer uses can be set to > tick at a rate a fine as one kilohertz, so that software engineers can > control the scheduling of tasks with precision."
> The promise of the high-res timer patch was usec resolution, not msec. > This would be a great loss. Does anybody know any more? Yes unfortunately it is true what they say in the article. The current timer resolution is 1msec (HZ = 1024, so to be precise the resolution is (1/1024) sec). In short the story is as follows: Linus accepted the POSIX 1003.1b Section 14 (Clocks and Timers) API in kernel 2.6 but not yet it's implementation (patches available here http://high-res-timers.sourceforge.net/ ). This means that applications using the POSIX 1003.1b timer API can specify timing values nanosecond resolution but for now only msec resolution is provided. But when the Linus & co will let in the kernel the high-res timer implementation, those apps will instantly be able to achieve higher resolution without recompilation etc. Yes usec resolution would be handy for some audio apps but I for now I am happy of being able to achieve msec resolution in MIDI playback without resorting to the RTC device which cannot easily be shared. PS: in the article they talk about 4500usec worst case scheduling latency (= 4.5msec), seems a bit disappointing. I'm curious what they mean with worst case, which kind of test suites they used etc. 2.4 + some LL patches let you reliably work with sub 3msec BTW. Benno ------------------------------------------------- This mail sent through http://www.gardena.net