Gregory Price <gourry.memverge@xxxxxxxxx> writes: > v2: change memtier mutex to semaphore > add source-node relative weighting > add remaining mempolicy integration code > > = v2 Notes > > Developed in colaboration with original authors to deconflict > similar efforts to extend mempolicy to take weights directly. > > == Mutex to Semaphore change: > > The memory tiering subsystem is extended in this patch set to have > externally available information (weights), and therefore additional > controls need to be added to ensure values are not changed (or tiers > changed/added/removed) during various calculations. > > Since it is expected that many threads will be accessing this data > during allocations, a mutex is not appropriate. IIUC, this is a change for performance. If so, please show some performance data. > Since write-updates (weight changes, hotplug events) are rare events, > a simple rw semaphore is sufficient. > > == Source-node relative weighting: > > Tiers can now be weighted differently based on the node requesting > the weight. For example CPU-Nodes 0 and 1 may have different weights > for the same CXL memory tier, because topologically the number of > NUMA hops is greater (or any other physical topological difference > resulting in different effective latency or bandwidth values) > > 1. Set weights for DDR (tier4) and CXL(teir22) tiers. > echo source_node:weight > /path/to/interleave_weight If source_node is considered, why not consider target_node too? On a system with only 1 tier (DRAM), do you want weighted interleaving among NUMA nodes? If so, why tie weighted interleaving with memory tiers? Why not just introduce weighted interleaving for NUMA nodes? > # Set tier4 weight from node 0 to 85 > echo 0:85 > /sys/devices/virtual/memory_tiering/memory_tier4/interleave_weight > # Set tier4 weight from node 1 to 65 > echo 1:65 > /sys/devices/virtual/memory_tiering/memory_tier4/interleave_weight > # Set tier22 weight from node 0 to 15 > echo 0:15 > /sys/devices/virtual/memory_tiering/memory_tier22/interleave_weight > # Set tier22 weight from node 1 to 10 > echo 1:10 > /sys/devices/virtual/memory_tiering/memory_tier22/interleave_weight -- Best Regards, Huang, Ying
