Load control and intelligence in schedulers

[Geoff Kuenning]

Henry Spencer writes:

>The problem with being smart about giving higher priority to processes
>that do terminal i/o is that all sorts of interesting programs start
>sprouting unnecessary terminal i/o.  I know of one large, hard-crunching
>compiler [name deleted to protect the guilty] which put out a NUL to
>the terminal each time it read a line of source, to keep its priority
>nice and high.  Argh.
>
>I'm not saying it can't be done well, just that care is needed.  Terminal
>input should be considered much more significant than output, for purposes
>of scheduling.

Programs that try to outsmart schedulers can be a serious problem.
But I wasn't talking about rewarding terminal output.  It is terminal
*input* that drives user's perceptions of response times, and thus
that is the only way to get a big priority kick.  Naturally, nobody
wants to 'babysit' a compute-bound program by giving it a CR every
second or so to keep it going (especially since a proper
implementation would ensure that only blocking reads gave the
priority boost).
-- 
	Geoff Kuenning
	First Systems Corporation
	...!ihnp4!trwrb!desint!geoff