From owner-freebsd-stable Mon Apr 20 12:46:42 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id MAA25965 for freebsd-stable-outgoing; Mon, 20 Apr 1998 12:46:42 -0700 (PDT) (envelope-from owner-freebsd-stable@FreeBSD.ORG) Received: from dyson.iquest.net (dyson.iquest.net [198.70.144.127]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id TAA25907; Mon, 20 Apr 1998 19:46:13 GMT (envelope-from toor@dyson.iquest.net) Received: (from root@localhost) by dyson.iquest.net (8.8.8/8.8.8) id OAA02812; Mon, 20 Apr 1998 14:44:05 -0500 (EST) (envelope-from toor) From: "John S. Dyson" Message-Id: <199804201944.OAA02812@dyson.iquest.net> Subject: Re: best wdc0 flags ? In-Reply-To: <199804201605.CAA04114@godzilla.zeta.org.au> from Bruce Evans at "Apr 21, 98 02:05:03 am" To: bde@zeta.org.au (Bruce Evans) Date: Mon, 20 Apr 1998 14:44:05 -0500 (EST) Cc: bde@zeta.org.au, mike@smith.net.au, dburr@POBoxes.com, hardware@FreeBSD.ORG, stable@FreeBSD.ORG, Studded@san.rr.com X-Mailer: ELM [version 2.4ME+ PL38 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk > >> > I tried those flags and noticed that it turned on 32-bit transfers for > >> >my wd0, resulting in a 20% increase in throughput. Out of curiosity, why > >> >aren't these flags included in GENERIC? > >> > >> Becuase they break operation of drives that don't support them. > > > >Do we have any examples of controllers that don't? > > I thought I did, but my oldest accessible drive (all 400MB of it from > 4 years ago) supports them. The probe seems to handle any that don't. > > Setting the multi-block flag is not such a good optimization, since it > pessimizes throughput on some drives and it increases interrupt latency. > What about defaulting to multi-block 4 instead of maximum. This would help the latency issue (re: 16), and mitigate alot of the CPU performance issues (re: 1)? John To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message