Re: [rfc 2/2] smaps: Show zone device memory used

[Balbir Singh <bsingharora@gmail.com>]

On Thu, 2017-10-19 at 13:02 -0400, Jerome Glisse wrote:
> On Thu, Oct 19, 2017 at 06:48:58AM +1100, Balbir Singh wrote:
> > On Wed, 18 Oct 2017 12:40:43 +0530
> > Anshuman Khandual <khandual@linux.vnet.ibm.com> wrote:
> > 
> > > On 10/18/2017 12:01 PM, Balbir Singh wrote:
> > > > With HMM, we can have either public or private zone
> > > > device pages. With private zone device pages, they should
> > > > show up as swapped entities. For public zone device pages  
> > > 
> > > Might be missing something here but why they should show up
> > > as swapped entities ? Could you please elaborate.
> > > 
> > 
> > For migrated entries, my use case is to
> > 
> > 1. malloc()/mmap() memory
> > 2. call migrate_vma()
> > 3. Look at smaps
> > 
> > It's probably not clear in the changelog.
> 
> My only worry is about API, is smaps consider as userspace API ?

Yes, do you think choosing DevicePublicMemory would help?

> My fear here is that maybe we will want to report device memory
> differently in the future and have different category of device

You are right, things will change and we'll probably see more things
in ZONE_DEVICE, but I am not sure how they'd show up in smaps or
can't think of it at the moment. The reason for my patch is was
that I expect only device public memory to have a need to be
visible in smaps as we do migration from regular memory to device
public memory and vice-versa.

> memory. Even thought right now i can only think of wanting to
> differentiate between public and private device memory but right
> now as you pointed out this is reported as swap out.
> 
> Otherwise patches looks good and you got:
> 
> Reviewed-by: JA(C)rA'me Glisse <jglisse@redhat.com>

Thank you.

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