Re: pci_map_sg() does not coalesce adjacent physical memory? x86

[Tejun Heo]

Leon Woestenberg wrote:
> Hello,
> 
> On Wed, Nov 19, 2008 at 8:58 AM, FUJITA Tomonori
> <fujita.tomonori@xxxxxxxxxxxxx> wrote:
>> On Wed, 19 Nov 2008 15:58:12 +0900
>> FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> 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
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