Nouveau - Nov 2020 - [PATCH v3 3/6] mm: support THP migration to device private memory

I hate the extra pin count magic here.  IMHO we really need to finish
off the series to get rid of the extra references on the ZONE_DEVICE
pages first.

On 11/6/20 12:03 AM, Christoph Hellwig wrote:
> I hate the extra pin count magic here.  IMHO we really need to finish
> off the series to get rid of the extra references on the ZONE_DEVICE
> pages first.
First, thanks for the review comments.

I don't like the extra refcount either, that is why I tried to fix that up
before resending this series. However, you didn't like me just fixing the
refcount only for device private pages and I don't know the dax/pmem code
and peer-to-peer PCIe uses of ZONE_DEVICE pages well enough to say how
long it will take me to fix all the use cases.
So I wanted to make progress on the THP migration code in the mean time.

On Fri, Nov 06, 2020 at 01:26:50PM -0800, Ralph Campbell
wrote:
>
> On 11/6/20 12:03 AM, Christoph Hellwig wrote:
>> I hate the extra pin count magic here.  IMHO we really need to finish
>> off the series to get rid of the extra references on the ZONE_DEVICE
>> pages first.
>
> First, thanks for the review comments.
>
> I don't like the extra refcount either, that is why I tried to fix that
up
> before resending this series. However, you didn't like me just fixing
the
> refcount only for device private pages and I don't know the dax/pmem
code
> and peer-to-peer PCIe uses of ZONE_DEVICE pages well enough to say how
> long it will take me to fix all the use cases.
> So I wanted to make progress on the THP migration code in the mean time.
I think P2P is pretty trivial, given that ZONE_DEVICE pages are used like
a normal memory allocator.  DAX is the interesting case, any specific
help that you need with that?