On Sun, Sep 10, 2017 at 07:22:58AM +0800, Bob Liu wrote:

On Wed, Sep 6, 2017 at 3:36 AM, Jerome Glisse [off-list ref] wrote:

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On Thu, Jul 20, 2017 at 08:48:20PM -0700, Dan Williams wrote:

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On Thu, Jul 20, 2017 at 6:41 PM, Jerome Glisse [off-list ref] wrote:

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On Fri, Jul 21, 2017 at 09:15:29AM +0800, Bob Liu wrote:

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On 2017/7/20 23:03, Jerome Glisse wrote:

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On Wed, Jul 19, 2017 at 05:09:04PM +0800, Bob Liu wrote:

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On 2017/7/19 10:25, Jerome Glisse wrote:

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On Wed, Jul 19, 2017 at 09:46:10AM +0800, Bob Liu wrote:

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On 2017/7/18 23:38, Jerome Glisse wrote:

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On Tue, Jul 18, 2017 at 11:26:51AM +0800, Bob Liu wrote:

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On 2017/7/14 5:15, Jerome Glisse wrote:

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Second device driver are not integrated that closely within mm and the
scheduler kernel code to allow to efficiently plug in device access
notification to page (ie to update struct page so that numa worker
thread can migrate memory base on accurate informations).

Third it can be hard to decide who win between CPU and device access
when it comes to updating thing like last CPU id.

Fourth there is no such thing like device id ie equivalent of CPU id.
If we were to add something the CPU id field in flags of struct page
would not be big enough so this can have repercusion on struct page
size. This is not an easy sell.

They are other issues i can't think of right now. I think for now it

My opinion is most of the issues are the same no matter use CDM or HMM-CDM.
I just care about a more complete solution no matter CDM,HMM-CDM or other ways.
HMM or HMM-CDM depends on device driver, but haven't see a public/full driver to
demonstrate the whole solution works fine.

I am working with NVidia close source driver team to make sure that it works
well for them. I am also working on nouveau open source driver for same NVidia
hardware thought it will be of less use as what is missing there is a solid
open source userspace to leverage this. Nonetheless open source driver are in
the work.

Can you point to the nouveau patches? I still find these HMM patches
un-reviewable without an upstream consumer.

So i pushed a branch with WIP for nouveau to use HMM:

https://cgit.freedesktop.org/~glisse/linux/log/?h=hmm-nouveau

Nice to see that.
Btw, do you have any plan for a CDM-HMM driver? CPU can write to
Device memory directly without extra copy.

Yes nouveau CDM support on PPC (which is the only CDM platform commercialy
available today) is on the TODO list. Note that the driver changes for CDM
are minimal (probably less than 100 lines of code). From the driver point
of view this is memory and it doesn't matter if it is CDM or not.

The real burden is on the application developpers who need to update their
code to leverage this.


Also as a data point you want to avoid CPU access to CDM device memory as
much as possible. The overhead for single cache line access are high (this
is PCIE or derivative protocol and it is a packet protocol).

Cheers,
Jerome

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