From owner-freebsd-hackers Thu Jul 2 06:35:06 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id GAA21656 for freebsd-hackers-outgoing; Thu, 2 Jul 1998 06:35:06 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from oslo.geco-prakla.slb.com (geos01.oslo.geco-prakla.slb.com [134.32.44.131]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id GAA21618; Thu, 2 Jul 1998 06:34:45 -0700 (PDT) (envelope-from smoergrd@geos01.oslo.geco-prakla.slb.com) Received: from sunw132.geco-prakla.slb.com (sunw132 [134.32.45.120]) by oslo.geco-prakla.slb.com (8.8.8/8.6.9) with SMTP id PAA04489 ; Thu, 2 Jul 1998 15:34:08 +0200 (MET DST) Received: by sunw132.geco-prakla.slb.com (SMI-8.6/SMI-SVR4) id PAA08137; Thu, 2 Jul 1998 15:34:08 +0200 To: Luigi Rizzo Cc: sos@FreeBSD.ORG, nick.hibma@jrc.it, hackers@FreeBSD.ORG Subject: Re: timeout granularity (was: Re: Console driver...) References: <199807021159.NAA12433@labinfo.iet.unipi.it> Organization: Schlumberger Geco-Prakla X-Disclaimer: I speak only for myself. From: smoergrd@oslo.geco-prakla.slb.com (Dag-Erling Coidan Smørgrav) Date: 02 Jul 1998 15:34:07 +0200 In-Reply-To: Luigi Rizzo's message of Thu, 2 Jul 1998 13:59:19 +0200 (MET DST) Message-ID: Lines: 20 X-Mailer: Gnus v5.3/Emacs 19.34 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Luigi Rizzo 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