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Date: Wed, 15 Oct 2003 21:51:34 -0700
From: "David S. Miller" <davem@redhat.com>
To: <mika.penttila@kolumbus.fi>
Cc: herbert@gondor.apana.org.au, torvalds@osdl.org, hch@infradead.org,
       axboe@suse.de, linux-kernel@vger.kernel.org
Subject: Re: [SCSI] Set max_phys_segments to sg_tablesize
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On Wed, 15 Oct 2003 15:37:22 +0300
<mika.penttila@kolumbus.fi> wrote:

> >It does matter if the driver can't cope with it.
> 
> But this fix may hurt performance with well behaving drivers in
> iommu systems. It's better to fix the broken drivers I think. 

That's absolutely correct.

If you add Herbert's change, you will effectively turn off all
of the IOMMU coalescing benefits we designed into the block layer.
Please don't apply it, fix the broken drivers instead.