Date: 02 Jul 1998 15:34:07 +0200 From: smoergrd@oslo.geco-prakla.slb.com (Dag-Erling Coidan Smørgrav) To: Luigi Rizzo <luigi@labinfo.iet.unipi.it> Cc: sos@FreeBSD.ORG, nick.hibma@jrc.it, hackers@FreeBSD.ORG Subject: Re: timeout granularity (was: Re: Console driver...) Message-ID: <rx4af6s2x80.fsf@oslo.geco-prakla.slb.com> In-Reply-To: Luigi Rizzo's message of Thu, 2 Jul 1998 13:59:19 %2B0200 (MET DST) References: <199807021159.NAA12433@labinfo.iet.unipi.it>
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Luigi Rizzo <luigi@labinfo.iet.unipi.it> writes: > > It's not that simple. You have to know how long to wait, which is > > practically impossible to do without hooking the timer interrupt and > > reprogramming it to keep pace with the retrace, and even that is > > difficult to achieve without a little busy-waiting here and there. > a little busy waiting is not a lot. What is bad is 10ms waiting With a 70 Hz refresh rate, we're talking more like 14 ms in the worst case, which is pretty darn bad. > If one can, say, assume that the vertical retrace is never less than > 1ms, then HZ=2000 should do the job (wakeup at every tick...). Ah, I didn't think of it quite like that. Yes, it would work, and you wouldn't have to busy-wait at all; just wake up at every tick, check if you're in a retrace, and if you are, do your job. DES -- Dag-Erling Smørgrav - smoergrd@oslo.geco-prakla.slb.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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