On Thu, Apr 14, 2022 at 03:09:42PM +0800, ying.huang@xxxxxxxxx wrote: > On Wed, 2022-04-13 at 14:52 +0530, Jagdish Gediya wrote: > > Sharing used_targets between multiple nodes in a single > > pass limits some of the opportunities for demotion target > > sharing. > > > > Don't share the used targets between multiple nodes in a > > single pass, instead accumulate all the used targets in > > source nodes shared by all pass, and reset 'used_targets' > > to source nodes while finding demotion targets for any new > > node. > > > > This results into some more opportunities to share demotion > > targets between multiple source nodes, 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 4 > > 3 4 > > 4 X > > > > e.g. with below NUMA topology, where node 0, 1 & 2 are > > cpu + dram nodes and node 3 is slow memory node, > > > > available: 4 nodes (0-3) > > 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: 4 5 > > node 2 size: n MB > > node 2 free: n MB > > node 3 cpus: > > node 3 size: n MB > > node 3 free: n MB > > node distances: > > node 0 1 2 3 > > 0: 10 20 20 40 > > 1: 20 10 20 40 > > 2: 20 20 10 40 > > 3: 40 40 40 10 > > > > The existing implementation gives below demotion targets, > > > > node demotion_target > > 0 3 > > 1 X > > 2 X > > 3 X > > > > With this patch applied, below are the demotion targets, > > > > node demotion_target > > 0 3 > > 1 3 > > 2 3 > > 3 X > > > > With the [PATCH v1], you have describe the demotion order changes for > the following system, I guess there's no change with [PATCH v2]? Yes, there is no change with v2. > With below NUMA topology, where node 0 & 2 are cpu + dram > nodes and node 1 & 3 are slow memory nodes, > > available: 4 nodes (0-3) > node 0 cpus: 0 1 > node 0 size: n MB > node 0 free: n MB > node 1 cpus: > node 1 size: n MB > node 1 free: n MB > node 2 cpus: 2 3 > node 2 size: n MB > node 2 free: n MB > node 3 cpus: > node 3 size: n MB > node 3 free: n MB > node distances: > node 0 1 2 3 > 0: 10 40 20 80 > 1: 40 10 80 80 > 2: 20 80 10 40 > 3: 80 80 40 10 > > And, what is the demotion order for the following system with [PATCH > v2]? > > Node 0 & 2 are cpu + dram nodes and node 1 are slow > memory node near node 0, > > available: 3 nodes (0-2) > node 0 cpus: 0 1 > node 0 size: n MB > node 0 free: n MB > node 1 cpus: > node 1 size: n MB > node 1 free: n MB > node 2 cpus: 2 3 > node 2 size: n MB > node 2 free: n MB > node distances: > node 0 1 2 > 0: 10 40 20 > 1: 40 10 80 > 2: 20 80 10 node 1 is demotion target for both node 0 and node 2 with this patch. node 1 is demotion target only for node 0 with existing implementation, however if node 1 is near to node 2 instead of node 0, still existing implementation will give node 1 as demotion target only for node 0 which is not the correct behavior. for both the scenario, with this patch applied, node 1 will be demotion target for both 0 and 2. > Best Regards, > Huang, Ying > > > [snip] > > > Best regards, Jagdish
