Re: [RFC 0/4] RFC - Coherent Device Memory (Not for inclusion)

[Reza Arbab <arbab@linux.vnet.ibm.com>]

On Mon, May 01, 2017 at 04:58:14PM -0700, John Hubbard wrote:
>On 05/01/2017 04:51 PM, Reza Arbab wrote:
>>On Mon, May 01, 2017 at 02:56:34PM -0700, John Hubbard wrote:
>>>On 05/01/2017 02:04 PM, Reza Arbab wrote:
>>>>On Mon, May 01, 2017 at 01:41:55PM -0700, John Hubbard wrote:
>>>>>1. A way to move pages between NUMA nodes, both virtual 
>>>>>address and physical address-based, from kernel mode.
>>>>
>>>>Jerome's migrate_vma() and migrate_dma() should have this 
>>>>covered, including DMA-accelerated copy.
>>>
>>>Yes, that's good. I wasn't sure from this discussion here if 
>>>either or both of those would be used, but now I see.
>>>
>>>Are those APIs ready for moving pages between NUMA nodes? As there 
>>>is no NUMA node id in the API, are we relying on the pages' 
>>>membership (using each page and updating which node it is on)?
>>
>>Yes. Those APIs work by callback. The alloc_and_copy() function you 
>>provide will be called at the appropriate point in the migration. 
>>Yours would allocate from a specific destination node, and copy 
>>using DMA.
>>
>
>hmmm, that reminds me: the whole story of "which device is this, and 
>which NUMA node does it correlate to?" will have to be wired up. That 
>is *probably* all in the device driver, but since I haven't worked 
>through it, I'd be inclined to list it as an item on the checklist, 
>just in case it requires some little hook in the upstream kernel.

I've worked this out. It can be contained to the driver itself.

-- 
Reza Arbab

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