Date: Mon, 20 Apr 1998 14:44:05 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: bde@zeta.org.au (Bruce Evans) Cc: bde@zeta.org.au, mike@smith.net.au, dburr@POBoxes.com, hardware@FreeBSD.ORG, stable@FreeBSD.ORG, Studded@san.rr.com Subject: Re: best wdc0 flags ? Message-ID: <199804201944.OAA02812@dyson.iquest.net> In-Reply-To: <199804201605.CAA04114@godzilla.zeta.org.au> from Bruce Evans at "Apr 21, 98 02:05:03 am"
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> >> > 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-hardware" in the body of the message
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