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Date:      Sun, 2 Aug 1998 23:04:01 +0100 (BST)
From:      Jose Marques <jose@nobody.org>
To:        freebsd-stable@FreeBSD.ORG, freebsd-mobile@FreeBSD.ORG
Subject:   wd driver multi-sector I/O and laptops
Message-ID:  <Pine.BSF.3.96.980802230319.242A-100000@nohow.demon.co.uk>

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I am running FreeBSD 2.2.7-stable (last updated on August 1st) on a
Toshiba Libretto 70CT.  I have replaced the supplied HD with a bigger
3.2GB Hitachi unit.  I have been playing with the "32-bit" and
"multi-sector transfer" options of the wd driver.  I have the following in
my kernel config file:

 controller      wdc0 at isa? port "IO_WD1" bio irq 14 vector wdintr
 disk            wd0 at wdc0 drive 0 flags 0x80ff

This produces the following probe message:

 wdc0 at 0x1f0-0x1f7 irq 14 on isa
 wdc0: unit 0 (wd0): <HITACHI_DK237A-32>, 32-bit, multi-block-16
 wd0: 3102MB (6354432 sectors), 6304 cyls, 16 heads, 63 S/T, 512 B/S

Using iozone before and after I see a great improvement in sequential
access.  The only problem occurs when I suspend my laptop and then resume.
If I resume from RAM I have no problem, however, if I resume from disk
then I see the following error almost immediately after the system has
resumed:

 wd0s2f: reverting to non-multi sector mode writing fsbn 65776 of
 65776-65791 (wd0s2 bn 1761520; cn 218 tn 56 sn 40)wd0: status 
 51<rdy,seekdone,err> error 4<abort>

Running iozone after this shows that performance has dropped to the level
when not using multi-sector transfers.  I have tried using 0xc0ff
(suspend-hack) but the problem still occurs.  Looking at the file
"/sys/i386/isa/wd.c" I notice that the driver turns off multi-sector i/o
on any such error.  I was wondering if it was "safe" to stop it doing
this.  Alternatively does the problem I describe above constitute a "bug" 
that I should report - or is it meant to behave that way.  Thanks in
advance for any advice.

-- 
Jose Marques


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