Re: [PATCH v5 1/9] mm/demotion: Add support for explicit memory tiers

[Aneesh Kumar K V]

On 6/14/22 10:15 PM, Jonathan Cameron wrote:
> 

...

>>
>> It could be simple tier0, tier1, tier2 numbering again, but the
>> numbers now would mean something to the user. A rank tunable is no
>> longer necessary.
> 
> This feels like it might make tier assignments a bit less stable
> and hence run into question of how to hook up accounting. Not my
> area of expertise though, but it was put forward as one of the reasons
> we didn't want hotplug to potentially end up shuffling other tiers
> around.  The desire was for a 'stable' entity.  Can avoid that with
> 'space' between them but then we sort of still have rank, just in a
> form that makes updating it messy (need to create a new tier to do
> it).
> 
>>

How about we do what is proposed here 

https://lore.kernel.org/linux-mm/7b72ccf4-f4ae-cb4e-f411-74d055482026@xxxxxxxxxxxxx

The cgroup accounting patch posted here https://lore.kernel.org/linux-mm/cover.1655242024.git.tim.c.chen@xxxxxxxxxxxxxxx

looks at top tier accounting per cgroup and I am not sure what tier ID stability is expected
for top tier accounting. 

-aneesh