"Huang, Ying" <ying.huang@xxxxxxxxx> writes: > Hi, Jagdish, > > Jagdish Gediya <jvgediya@xxxxxxxxxxxxx> writes: > ... >> e.g. with below NUMA topology, where node 0 & 1 are >> cpu + dram nodes, node 2 & 3 are equally slower memory >> only nodes, and node 4 is slowest memory only node, >> >> available: 5 nodes (0-4) >> node 0 cpus: 0 1 >> node 0 size: n MB >> node 0 free: n MB >> node 1 cpus: 2 3 >> node 1 size: n MB >> node 1 free: n MB >> node 2 cpus: >> node 2 size: n MB >> node 2 free: n MB >> node 3 cpus: >> node 3 size: n MB >> node 3 free: n MB >> node 4 cpus: >> node 4 size: n MB >> node 4 free: n MB >> node distances: >> node 0 1 2 3 4 >> 0: 10 20 40 40 80 >> 1: 20 10 40 40 80 >> 2: 40 40 10 40 80 >> 3: 40 40 40 10 80 >> 4: 80 80 80 80 10 >> >> The existing implementation gives below demotion targets, >> >> node demotion_target >> 0 3, 2 >> 1 4 >> 2 X >> 3 X >> 4 X >> >> With this patch applied, below are the demotion targets, >> >> node demotion_target >> 0 3, 2 >> 1 3, 2 >> 2 3 >> 3 4 >> 4 X > > For such machine, I think the perfect demotion order is, > > node demotion_target > 0 2, 3 > 1 2, 3 > 2 4 > 3 4 > 4 X I guess the "equally slow nodes" is a confusing definition here. Now if the system consists of 2 1GB equally slow memory and the firmware doesn't want to differentiate between them, firmware can present a single NUMA node with 2GB capacity? The fact that we are finding two NUMA nodes is a hint that there is some difference between these two memory devices. This is also captured by the fact that the distance between 2 and 3 is 40 and not 10. For that specific topology where the distance between 2 and 3 is 40 and 2 and 4 is 80, the demotion target derived by the new code is better right? ... -aneesh
