Re: [Haskell-cafe] Precise timing

I think threadDelay is the wrong operation here. Its fundamentally a primitive for **spreading out** compute, rather than *scheduling compute*. one (crazy) idea might be the following, say you wanna do an event every X milli seconds (with some error tolerance about the precise timing), do a threadDelay for 1/2-2/3rds X, then poll the time constantly :) OTOH, as other folks are suggesting, theres probably fundamentally better primitives already available. On Sun, Oct 19, 2014 at 5:11 PM, Brandon Allbery wrote:

On Sun, Oct 19, 2014 at 3:44 PM, Jeffrey Brown wrote:

...

You mean I should call chrt from the command line after starting the process, to modify its priority?

Normally you'd use it to run the program. But, as I said at least twice, it's Linux specific.

...

This documentation http://hackage.haskell.org/package/posix-realtime-0.0.0.1/src/System/Posix/R... for the posix-realtime package https://hackage.haskell.org/package/posix-realtime says that it has a sched_setscheduler function. That supposedly exists on my OS (OS X 10.9). The chrt command, on the other hand,

Does it warn you that you need privileges (probably root) to switch to a higher scheduler level? Normally realtime and other high priority schedulers require elevated privileges, whereas lower priority schedulers such as SCHED_IDLE don't.

I should note that I see no manpage for sched_setscheduler on 10.9.5, nor do I find it in any of the dylibs in /usr/lib.

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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