Messages in this thread | | | Date | Thu, 28 Jul 2005 09:22:10 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable |
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* Steven Rostedt <rostedt@goodmis.org> wrote:
> A colleague of mine, well actually the VP of my company of the time, > Doug Locke, gave me a perfect example. If you have a program that > runs a nuclear power plant that needs to wake up and run 4 seconds > every 10 seconds, and on that same computer you have a program running > a washing machine that needs to wake up every 3 seconds and run for > one second (I'm using seconds just to make the example simple). Which > process gets the higher priority? The answer is the washing machine. > > Rational: If the power plant was higher priority, the washing machine > would fail almost every time, since the power plant program would run > for 4 seconds, and since the cycle of the washing machine is 3 > seconds, it would fail everytime the nuclear power plant program ran. > Now if you have the washing machine run in it's cycle, the nuclear > power plant can easily make the 4 seconds ever 10 seconds, even when > it is interrupted by the washing machine.
nitpicking: i guess the answer also depends on what the precise requirement is. If the requirement is 'run for 4 seconds every 10 seconds, uninterrupted, else the power plant melts down', i'd sure not make the washing machine process the higher priority one ;-)
(also, i'd give the power plant process higher priority even if the requirement is not as strict, just from a risk POV: what if the washing machine control program is buggy and got into an infinite loop somewhere.)
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