On Thu, May 12, 2022 at 12:12 AM Aneesh Kumar K V <aneesh.kumar@xxxxxxxxxxxxx> 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 > > -aneesh It is harder to implement memtierN as just a file and doesn't follow the existing sysfs pattern, either. Besides, it is extensible to have memtierN as a directory.
