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Date: Sat, 19 Jan 2002 12:36:52 -0800 (PST)
From: Andre Hedrick <andre@linuxdiskcert.org>
To: Jens Axboe <axboe@suse.de>
cc: Davide Libenzi <davidel@xmailserver.org>,
        Anton Altaparmakov <aia21@cam.ac.uk>,
        Linus Torvalds <torvalds@transmeta.com>,
        lkml <linux-kernel@vger.kernel.org>
Subject: Re: Linux 2.5.3-pre1-aia1
In-Reply-To: <20020119164503.H27835@suse.de>
Message-ID: <Pine.LNX.4.10.10201191220060.7770-100000@master.linux-ide.org>
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On Sat, 19 Jan 2002, Jens Axboe wrote:

> On Sat, Jan 19 2002, Andre Hedrick wrote:
> > On Sat, 19 Jan 2002, Jens Axboe wrote:
> > 
> > > On Fri, Jan 18 2002, Davide Libenzi wrote:
> > > > Guys, instead of requiring an -m8 to every user that is observing this
> > > > problem, isn't it better that you limit it inside the driver until things
> > > > gets fixed ?
> > > 
> > > There is no -m8 limit, 2.5.3-pre1 + ata253p1-2 patch handles any set
> > > multi mode value.
> > > 
> > > -- 
> > > Jens Axboe
> > > 
> > 
> > And that will generate the [lost interrupt], and I have it fixed at all
> > levels too now.
> 
> How so? I don't see the problem.

Unlike ATAPI which will generally send you more data than requested on
itw own, ATA devices do not like enjoy or play the game.  Additionally the
current code asks for 16 sectors, but we do not do the request copy
anymore, and this mean for every 4k of paging we are soliciting for 8k.
We only read out 4k thus the device has the the next 4k we may be wanting
ready.  Look at it as a dirty prefetch, but eventally the drive is going
to want to go south, thus [lost interrupt]

Basically as the Block maintainer, you pointed out I am restricted to 4k
chunking in PIO.  You decided, in the interest of the block glue layer
into the driver, to force early end request per Linus's requirements to
return back every 4k completed to block regardless of the size of the
total data requested.

For the above two condition to be properly satisfied, I have to adjust
and apply one driver policy make the driver behave and give the desired
results.  We should note this will conform with future IDEMA proposals
being submitted to the T committees.

Regards,

Andre Hedrick
Linux Disk Certification Project                Linux ATA Development

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