Moshe Nissim (moshe++at++orad.co.il)
Tue, 30 Mar 1999 10:45:11 +0200
>
> The timer intervals are 10ms for non-realtime processes, and FASTHZ for
> realtime. The value for FASTHZ is very system dependent. On Onyx2, its
> about 800nsec and for Onyx, I believe its 21nsec.
>
'systune fasthz' on 6.5.2 gives 1000
This is the default setting in the 6.5.2-distributed /var/sysgen/mtune/kernel file.
So how did the 800nsec pop up?
21 nsec?? Is this a typo?
>
> > Also when the time-slice is 1ms there is an extra slice of sleep. Thus you get
> > 11 ms from sginap.
>
> The semantic is (and was supposed to have been) that you will sleep for
> at least the time requested.
Imagine sleep(1) returning after one minute :)
> The scheduling logic chose to awaken
> non-realtime processes at the next clock tick (10msec) after the
> interval has expired.
Then this is a definite change from pre 6.5 itimer logic.
> For realtime processes, again the sleep will last at least the interval
> requested, but the wakeup will occur at the next fasthz tick following
> expiration.
>
Again, a change from pre 6.5 logic.
>
> This is not a scheduling problem. The old behaviour (sleep for at most
> the duration of the interval) was actually incorrect and Performer
> depended upon that incorrectness.
I suspect other programs out there depended on that 'incorrectness' as well.
Bye,
Moshe
-- Moshe Nissim, Orad Hi-Tec Systems Tel: (972) - 9 - 7676862 (ext. 579) Fax: (972) - 9 - 7676861 Email: moshe++at++orad.co.il
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