Messages in this thread | | | Date | Sat, 10 Jul 1999 22:56:04 +0200 (CEST) | From | Rik van Riel <> | Subject | Re: Can't sleep less than 20 ms |
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On Fri, 9 Jul 1999, Jamie Lokier wrote: > Matti Aarnio wrote: > > > I'd rather see: > > > > > > - slow HZ -- low interrupt load > > > - accurate timers on demand > > > - *precise* timing with accuracy of hardware > > > > RTC based interrupts ? Highly accurate periodic interrupts, > > not re-sceduling based "regular by luck"... > > I'd like "regular by design".
:)
> Note that RTC interrupts are just as inaccurate for user space > apps than 8253-based accurate timers -- the scheduling overhead > and lack of guarantee is still present.
- RTC interrupts can be delivered on any 'wanted' time, not just on 10ms marks - the lack of guarantee isn't that bad for 99% of applications (multimedia and related stuff) - using a decent timer will improve multimedia performance - having a decent timer will/might allow us to better pinpoint the cause of the lack of guarantee - the scheduling overhead is very small already
Maybe we want a special 'multimedia' scheduling mode with these properties: - able to ask for rescheduling on RTC interrupts - CPU time is twice as expensive - priority is higher, but the process gets less CPU to hog
This way, multimedia programmers are encouraged to code their program with one 'worker' thread and one 'output' thread -- with some buffering in between to catch most I/O delays etc...
For real RT or low-latency work, you will need to work on an unloaded computer anyway.
Rik -- Open Source: you deserve to be in control of your data. +-------------------------------------------------------------------+ | Le Reseau netwerksystemen BV: http://www.reseau.nl/ | | Linux Memory Management site: http://www.linux.eu.org/Linux-MM/ | | Nederlandse Linux documentatie: http://www.nl.linux.org/ | +-------------------------------------------------------------------+
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