linux-kernel - Re: more iommu sg merging fallout

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Message-Id: <20080206.160147.25411834.davem@davemloft.net>
Date:	Wed, 06 Feb 2008 16:01:47 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	fujita.tomonori@....ntt.co.jp
Cc:	tomof@....org, jens.axboe@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: more iommu sg merging fallout

From: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Date: Thu, 07 Feb 2008 08:53:33 +0900

> On Wed, 06 Feb 2008 15:18:55 -0800 (PST)
> David Miller <davem@...emloft.net> wrote:
> 
> > I intend to put merging back in, perhaps something similar to
> > powerpc's merging logic but without the expensive (in my opinion)
> > IOMMU allocation every loop.  I think it is better to determine the
> > segment breaks in one pass, allocate that many IOMMU entries in one
> > allocation, then fill them all in.
> 
> I thought about asking you if I can modify the SPARC IOMMUs to do
> allocation in every loop.
> 
> The reason why I need the allocation in every loop is that I also need
> to fix the problem that IOMMUs allocate memory areas without
> considering a low level driver's segment boundary limits.
> 
> http://linux.derkeiler.com/Mailing-Lists/Kernel/2007-11/msg07616.html
> http://linux.derkeiler.com/Mailing-Lists/Kernel/2007-12/msg02286.html
> 
> As far as I know, all the IOMMUs except for SPARC allocate a free area
> in every loop but if it's too expensive for SPARC, then we need to
> find a different way to handle segment boundary limits.

Ok then what I'll do is adopt some version of powerpc's merging
allocator into the sparc64 code.
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