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Re: Feature requests for sleep and a new program

From: Johannes Niess
Subject: Re: Feature requests for sleep and a new program
Date: 30 Nov 2001 09:24:15 +0100

Bob Proulx <address@hidden> writes:

> > Hi,
> > 
> > I'd like to propose two new features to "sleep":
> > 
> > 1) Sub-Second resolution
> GNU sleep version 2.0a and later implements that.  The NEWS file
> contains:
>  [2.0a]
>  * sleep accepts floating point arguments on command line

Sorry. I checked the production version. 


> You could 'time' the loop payload, extract the real time, subtract
> that from the desired loop time, guarentee that it is non-negative,
> sleep for that value.  Implementation left as an excercise to the
> reader.  :-) [Hint: The "time --format='%e\n'" option would probably
> be useful.]

Mostly correct. It does not account for the loop administration time
and the test function. Your approach is a lot more to type. The "sleep
-m" approach allows for a different way of thinking.

> > A new program could supplement "nice". In some (rare) cases you want
> > to control the maximum CPU load a program can generate. It could be
> > dome via signals. To allow a maximum CPU load of 0.5 for a program
> > you can send a TSTOP signal , wait 0.5 seconds, send CONT and wait
> > 0.5 seconds and so on.
> > 
> > I know that programs can intercept signals but it'll work for most
> > programs.
> low_priority_task_to_run &
> while sleep 0.5; do
>   kill -STOP $! || break
>   sleep 0.5
>   kill -CONT $! || break
> done
> Interesting...

That's what I'm doing to run setiathome on my laptop to keep the CPU
fan quiet. It's OK for non-interactive programms. But interactive
programms need much lower cycle times (e. g. 0.1 sec) to run
smoothly. This causes a lot of overhead to start the "sleep" binary
all the time. A C function is much cheaper resourcewise.

Johannes Nieß

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