From owner-cvs-all Sat Dec 22 19:44:26 2001 Delivered-To: cvs-all@freebsd.org Received: from root.com (root.com [209.102.106.178]) by hub.freebsd.org (Postfix) with ESMTP id 1484737B405; Sat, 22 Dec 2001 19:44:17 -0800 (PST) Received: (from dg@localhost) by root.com (8.11.2/8.11.2) id fBN3Yj724592; Sat, 22 Dec 2001 19:34:45 -0800 (PST) (envelope-from dg) Date: Sat, 22 Dec 2001 19:34:45 -0800 From: David Greenman To: Bruce Evans Cc: Mike Silbersack , Matt Dillon , cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/dev/sio sio.c Message-ID: <20011222193445.E24034@nexus.root.com> References: <20011222191321.B24034@nexus.root.com> <20011223143011.G10441-100000@gamplex.bde.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20011223143011.G10441-100000@gamplex.bde.org>; from bde@zeta.org.au on Sun, Dec 23, 2001 at 02:41:16PM +1100 Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG >On Sat, 22 Dec 2001, David Greenman wrote: > >> >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. :-) > >At least if they have been untouched for that long then they were probably >correct :-). Correct for the time, perhaps, but hardware has gotten faster and FreeBSD kernel latency has apparantly gotten worse. >> 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. > >I once planned to bring this back, at least as an option, with the >ratcheting down limited to 1 step. I never got around to this because >the problem seemed to have gone away except for unusual hardware >combinations. Perhaps reduce it to the mid-point (8), but not below that. -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