Date: Thu, 2 Jul 1998 13:59:19 +0200 (MET DST) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: smoergrd@oslo.geco-prakla.slb.com (Dag-Erling Coidan Smørgrav) Cc: sos@FreeBSD.ORG, nick.hibma@jrc.it, hackers@FreeBSD.ORG Subject: Re: timeout granularity (was: Re: Console driver...) Message-ID: <199807021159.NAA12433@labinfo.iet.unipi.it> In-Reply-To: <rx4emw42ya6.fsf@oslo.geco-prakla.slb.com> from "Dag-Erling Coidan Smørgrav" at Jul 2, 98 03:10:54 pm
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> > the code might check if HZ is set to a suitable value (how large, > > e.g. 1000 or 2000, i have no idea) and use timeout instead of > > polling if the test is successful. Sooner or later hopefully we > > will move to large values of HZ anyways. > > > > (or, how about adding a utimeout() call to the kernel :) > > 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 (I hope interrupts are enabled while waiting!) 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...). cheers -----------------------------+-------------------------------------- Luigi Rizzo | Dip. di Ingegneria dell'Informazione email: luigi@iet.unipi.it | Universita' di Pisa tel: +39-50-568533 | via Diotisalvi 2, 56126 PISA (Italy) fax: +39-50-568522 | http://www.iet.unipi.it/~luigi/ _____________________________|______________________________________ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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