Date: Sat, 22 Dec 2001 19:13:21 -0800 From: David Greenman <dg@root.com> To: Bruce Evans <bde@zeta.org.au> Cc: Mike Silbersack <silby@silby.com>, Matt Dillon <dillon@FreeBSD.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/dev/sio sio.c Message-ID: <20011222191321.B24034@nexus.root.com> In-Reply-To: <20011223135146.H10320-100000@gamplex.bde.org>; from bde@zeta.org.au on Sun, Dec 23, 2001 at 02:10:07PM %2B1100 References: <Pine.BSF.4.30.0112222142580.51733-100000@niwun.pair.com> <20011223135146.H10320-100000@gamplex.bde.org>
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>The driver used to have dynamic fifo trigger reduction, mainly to >support many active sio devices, but this was found harmful and backed >out: > >! RCS file: /home/ncvs/src/sys/dev/sio/sio.c,v >! Working file: sio.c >! head: 1.353 >! ... >! ---------------------------- >! revision 1.53 >! date: 1994/09/21 19:39:25; author: davidg; state: Exp; lines: +3 -1 >! #if 0'd evil dynamic fifo trigger level adjustment; it just bit me and >! a couple of other people again. >! ---------------------------- You know, it's really weird to see stuff that I wrote from more than 7 years ago. I can only imagine how Kirk feels when he sees log messages from the 80's. :-) As I recall, the dynamic adjustment increased interrupt overhead each time it ratcheted down, causing it to be even more likely to lower it further until it was "1", disabling the overhead reduction benefits of the fifo completely. The cure became worse than the disease. -DG David Greenman Co-founder, The FreeBSD Project - http://www.freebsd.org President, TeraSolutions, Inc. - http://www.terasolutions.com Pave the road of life with opportunities. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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