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Date: Mon, 18 Nov 2002 15:12:37 +0100
From: Jens Axboe <axboe@suse.de>
To: Stephen Lord <lord@sgi.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: SCSI I/O performance problems when CONFIG_HIGHIO is off
Message-ID: <20021118141237.GA1024@suse.de>
References: <1037392310.13531.419.camel@jen.americas.sgi.com> <20021118120531.GC839@suse.de> <1037628312.1680.5.camel@laptop.americas.sgi.com>
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On Mon, Nov 18 2002, Stephen Lord wrote:
> On Mon, 2002-11-18 at 06:05, Jens Axboe wrote:
> 
> > 
> > Steve,
> > 
> > Something isn't quite making sense. If we go over every single instance
> > of checking ->highmem_io, they all look sane (ie checking on non-highmem
> > setup must yield 0). So that part looks good.
> > 
> > However, I think a typo snuck in there, in exactly the spot you pasted
> > above. Could you try 2.4.20-rc2 with this patch applied?
> > 
> > ===== drivers/scsi/scsi_merge.c 1.9 vs edited =====
> > --- 1.9/drivers/scsi/scsi_merge.c	Mon Sep 16 09:25:10 2002
> > +++ edited/drivers/scsi/scsi_merge.c	Mon Nov 18 13:04:41 2002
> > @@ -835,7 +835,7 @@
> >  	 * case.
> >   	 */
> >  	if (count == 1 && !SCpnt->host->highmem_io) {
> > -		this_count = req->current_nr_sectors;
> > +		this_count = req->nr_sectors;
> >  		goto single_segment;
> >  	}
> 
> That looks like it does it, performance is pretty much what I was
> getting with HIGHIO on.

Great, thanks for verifying that. I'll push it to Marcelo ASAP.

-- 
Jens Axboe

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