On Thu, 2022-05-12 at 12:42 +0530, Aneesh Kumar K V wrote: > On 5/12/22 12:33 PM, ying.huang@xxxxxxxxx wrote: > > 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 ':' > > > > It will be really useful to fetch the memory tier node list in an easy > fashion rather than reading multiple sysfs directories. If we don't have > other attributes for memorytier, we could keep > "/sys/devices/system/memtier/memtierN" a NUMA node list there by > avoiding /sys/devices/system/memtier/memtierN/nodelist This will make the interface not extensible. Even a single file "/sys/devices/system/node/memtiers" is better. As an readonly file, it should be OK to put multiple values in it. I remember that one rule for sysfs is that it is accessed more via libsysfs. Does that make life easier? Best Regards, Huang, Ying
