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charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Dec 10, 2024 at 01:14:43AM +0100, Andrea Righi wrote: > > And altogether this should look like: > > > > int scx_pick_idle_cpu_from_hop(struct cpumask *hop_cpus, struct cpumask *cpus_allowed) > > { > > int node, cpu, random_cpu; > > > > do { > > > > /* Pick a 'random' CPU in the hop */ > > random_cpu = cpumask_any_and_distribute(hop_cpus, cpus_allowed); > > if (random_cpu >= nr_cpu_ids) > > continue; > > > > node = cpu_to_node(random_cpu); > > > > /* Find an idle CPU in the same node */ > > cpu = scx_pick_idle_cpu_from_node(node, cpus_allowed, flags); > > if (cpu >= 0) > > break; > > > > /* No luck? Try other nodes */ > > } while (cpumask_andnot(hop_cpus, hop_cpus, cpumask_of_node(node))); > > > > return cpu; > > } > > > > static s32 scx_pick_idle_cpu(const struct cpumask *cpus_allowed, s32 prev_cpu, u64 flags) > > { > > const struct cpumask *next, *prev = cpu_none_mask; > > int prev_node = cpu_to_node(prev_cpu); > > ... > > for_each_numa_hop_mask(next, prev_node) { > > cpumask_andnot(hop_cpus, next, prev); > > cpu = scx_pick_idle_cpu_from_hop(hop_cpus, cpus_allowed); > > prev = next; > > } > > ... > > } > > > > Not tested, but should work. > > Makes sense to me, I'll do some testing with this. One thing you can do to optimize it is introducing a function that pulls nodes from the hop_cpus: void sched_get_hop_nodes(nodemask_t *hop_nodes, const struct cpumask *hop_cpus) { int cpu; for_each_cpu(cpu, hop_cpus) { node_set(cpu_to_node(cpu);, hop_nodes); cpu = cpumask_next_zero(cpu, cpumask_of_node(node) } } This should be O(N), but it will let you to avoid O(N*M) in the loop condition inside scx_pick_idle_cpu_from_hop(): int scx_pick_idle_cpu_from_hop(nodemask_t *hop_nodes, struct cpumask *cpus_allowed) { int node, idle_cpu, random_cpu; for_each_node_mask(node, &hop_nodes) { /* Pick a 'random' CPU in the node */ random_cpu = cpumask_any_and_distribute(cpumask_of_node(node), cpus_allowed); if (random_cpu >= nr_cpu_ids) continue; /* Find an idle CPU in the same node */ idle_cpu = scx_pick_idle_cpu_from_node(node, cpus_allowed, flags); if (idle_cpu >= 0) break; } return cpu; } And at this point I'd also compare the above with non-randomized version: static s32 scx_pick_idle_cpu(const struct cpumask *cpus_allowed, s32 prev_cpu, u64 flags) { const struct cpumask *next, *prev = cpu_none_mask; int prev_node = cpu_to_node(prev_cpu); nodemask_t hop_nodes; ... for_each_numa_hop_mask(next, prev_node) { if (!cpumask_and_andnot(hop_cpus, next, cpus_allow, prev)) goto cont; sched_get_hop_nodes(hop_nodes, hop_cpus); for_each_node_mask(node, hop_nodes) { cpu = scx_pick_idle_cpu_from_node(node, cpus_allowed, flags); if (cpu >= 0) goto found; } cont: prev = next; } ... } Don't know how it works, but it looks really good. Thanks, Yury