Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory

Dan Williams
2017-04-20T00:07:58Z

On Wed, Apr 19, 2017 at 3:55 PM, Logan Gunthorpe <logang-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org> wrote:
>
>
> On 19/04/17 02:48 PM, Jason Gunthorpe wrote:
>> On Wed, Apr 19, 2017 at 01:41:49PM -0600, Logan Gunthorpe wrote:
>>
>>>> But.. it could point to a GPU and the GPU struct device could have a
>>>> proxy dma_ops like Dan pointed out.
>>>
>>> Seems a bit awkward to me that in order for the intended use case, you
>>> have to proxy the dma_ops. I'd probably still suggest throwing a couple
>>> ops for things like this in the dev_pagemap.
>>
>> Another option is adding a new 'struct completer_dma_ops *' to struct
>> device for this use case.
>>
>> Seems like a waste to expand dev_pagemap when we only need a unique
>> value per struct device?
>
> I feel like expanding dev_pagemap has a much lower impact than expanding
> struct device... dev_pagemap is only one instance per zone device region
> so expanding it shouldn't be a huge issue. Expanding struct device means
> every device struct in the system gets bigger.

Especially since we expect a very small subset of devices will ever support p2p.