Re: RFC: Memory Tiering Kernel Interfaces (v2)

[ying.huang@xxxxxxxxx]

On Wed, 2022-05-11 at 23:22 -0700, Wei Xu wrote:
> Sysfs Interfaces
> ================
> 
> * /sys/devices/system/memtier/memtierN/nodelist
> 
>   where N = 0, 1, 2 (the kernel supports only 3 tiers for now).
> 
>   Format: node_list
> 
>   Read-only.  When read, list the memory nodes in the specified tier.
> 
>   Tier 0 is the highest tier, while tier 2 is the lowest tier.
> 
>   The absolute value of a tier id number has no specific meaning.
>   What matters is the relative order of the tier id numbers.
> 
>   When a memory tier has no nodes, the kernel can hide its memtier
>   sysfs files.
> 
> * /sys/devices/system/node/nodeN/memtier
> 
>   where N = 0, 1, ...
> 
>   Format: int or empty
> 
>   When read, list the memory tier that the node belongs to.  Its value
>   is empty for a CPU-only NUMA node.
> 
>   When written, the kernel moves the node into the specified memory
>   tier if the move is allowed.  The tier assignment of all other nodes
>   are not affected.
> 
>   Initially, we can make this interface read-only.

It seems that "/sys/devices/system/node/nodeN/memtier" has all
information we needed.  Do we really need
"/sys/devices/system/memtier/memtierN/nodelist"?

That can be gotten via a simple shell command line,

$ grep . /sys/devices/system/node/nodeN/memtier | sort -n -k 2 -t ':'

Best Regards,
Huang, Ying