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From: Tejun Heo <tj@kernel.org>
To: Leon Woestenberg <leon.woestenberg@gmail.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
	jens.axboe@oracle.com, akpm@linux-foundation.org,
	linux-kernel@vger.kernel.org,
	James.Bottomley@hansenpartnership.com
Subject: Re: pci_map_sg() does not coalesce adjacent physical memory? x86
Date: Wed, 19 Nov 2008 19:05:09 +0900	[thread overview]
Message-ID: <4923E4D5.4070202@kernel.org> (raw)
In-Reply-To: <c384c5ea0811190145y78803fbboecfcf6ebd652ee03@mail.gmail.com>

Leon Woestenberg wrote:
> Hello,
> 
> On Wed, Nov 19, 2008 at 8:58 AM, FUJITA Tomonori
> <fujita.tomonori@lab.ntt.co.jp> wrote:
>> On Wed, 19 Nov 2008 15:58:12 +0900
>> FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
>>> On Wed, 19 Nov 2008 07:22:31 +0100
>> - pci_map_sg/dma_map_sg are used with a scatter gather list that
>> doesn't come from the block layer (e.g. some network drivers do).
>>
> This is the point I then want to make: we have pci_map_sg() users in
> other system than the block layer, the network and v4l2 subsystems,
> why cannot they benefit from coalescing?

Because pci_map_sg() doesn't know the memory access limits of the
controller as block layer does.

> Should they copy the block layer coalescing implementation, or should
> that implementation be made more generic and live outside the block
> sub system?

The latter sounds like a good idea to me.

Thanks.

-- 
tejun

      reply	other threads:[~2008-11-19 10:06 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-11-17 21:54 pci_map_sg() does not coalesce adjacent physical memory? x86 Leon Woestenberg
2008-11-18  3:15 ` Andrew Morton
2008-11-18  5:21   ` James Bottomley
2008-11-18  9:37     ` Leon Woestenberg
2008-11-19  5:19   ` FUJITA Tomonori
2008-11-19  6:22     ` Leon Woestenberg
2008-11-19  6:58       ` FUJITA Tomonori
2008-11-19  7:05         ` FUJITA Tomonori
2008-11-19  7:58         ` FUJITA Tomonori
2008-11-19  9:45           ` Leon Woestenberg
2008-11-19 10:05             ` Tejun Heo [this message]

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