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From: Simon Wright <simon@pogner.demon.co.uk>
Subject: Re: Timers in application (again)
Date: 2000/07/14
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Frode Tenneboe <ft@alne.edh.ericsson.se> writes:

> Ted Dennison <dennison@telepath.com> wrote:
> : Simon Wright wrote:
> 
> :> Solaris runs with 10 mS ticks out-of-the-box. You can easily set this (2.6
> :> and later) to 1 mS (set hires_tick to 1 in /etc/system).
> 
> : So both 20 and 50Hz should be achievable "out of the box". Frode can go check
> : /etc/system to see if the default has been modified.
> 
> The default has not been changed.
> 
> Would changing to a hires tick improve reliability when I don't want/need
> granularity of <10mS?
> 
> Must I run as root on solaris to get the expected behviour? It appears
> as it works better for root but I have not tested heavily.

If you use the default tick, you will delay (or delay until) for at
least 10 mS; in practice, this means 20 mS intervals, other things
being equal. If that's OK, fine.

Changing the tick doesn't cause any problems we are aware of, unlike
Linux where the system does seem a little inclined to lock up (once
per 3 weeks, perhaps) -- but the standard libraries weren't rebuilt,
so there may be some dependencies on the actual value of HZ
(<asm/param.h>).

With GNAT, a tasking program run as root will use the RT dispatching
class, and priorities will work. Run as any other user, priorities
will not work (and the OS will do its own round-robin or whatever
scheduling).