From owner-freebsd-stable  Mon Mar 12 13:20:45 2001
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From: Soren Schmidt <sos@freebsd.dk>
Message-Id: <200103122120.WAA10675@freebsd.dk>
Subject: Re: Disk I/O problem in 4.3-BETA
In-Reply-To: <20010312125905.X18351@fw.wintelcom.net> from Alfred Perlstein at "Mar 12, 2001 12:59:05 pm"
To: bright@wintelcom.net (Alfred Perlstein)
Date: Mon, 12 Mar 2001 22:20:32 +0100 (CET)
Cc: oberman@es.net (Kevin Oberman), mobile@FreeBSD.ORG,
	stable@FreeBSD.ORG
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It seems Alfred Perlstein wrote:
> > > Prior to March 1 I could dd a 4 GB slice in 580 seconds (or a bit
> > > under 10 minutes).  After March 1 the same exact command took just
> > > under 40 minutes to complete. The same was seen copying a 2 GB
> > > slice. It increased from 5 minutes to 20 minutes. No kernel
> > > configuration changes were made.
> > 
> > This is worse than expected, try to use option ATA_ENABLE_WC
> > and see what gives, if its not back to normal we have to look elsewhere.
> 
> Mr ATA, is there no ATA command to "syncronize cache" like in SCSI?

Yes, there is, and the ATA driver even uses it, the problem is WHEN
to use it. I originally made it flush the cache if a write contained
the BIO_ORDERED bit, but that doesn't work with softupdates..
If somebody can come up with a way to tell me when I need to flush
the write cache, then I'll happily add that..

-Søren

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