cpumask_local_spread() currently checks local node for presence of i'th CPU, and then if it finds nothing makes a flat search among all non-local CPUs. We can do it better by checking CPUs per NUMA hops. This series is inspired by Valentin Schneider's "net/mlx5e: Improve remote NUMA preferences used for the IRQ affinity hints" https://patchwork.kernel.org/project/netdevbpf/patch/20220728191203.4055-3-tariqt@xxxxxxxxxx/ According to Valentin's measurements, for mlx5e: Bottleneck in RX side is released, reached linerate (~1.8x speedup). ~30% less cpu util on TX. This patch makes cpumask_local_spread() traversing CPUs based on NUMA distance, just as well, and I expect comparabale improvement for its users, as in Valentin's case. I tested it on my VM with the following NUMA configuration: root@debian:~# numactl -H available: 4 nodes (0-3) node 0 cpus: 0 1 2 3 node 0 size: 3869 MB node 0 free: 3740 MB node 1 cpus: 4 5 node 1 size: 1969 MB node 1 free: 1937 MB node 2 cpus: 6 7 node 2 size: 1967 MB node 2 free: 1873 MB node 3 cpus: 8 9 10 11 12 13 14 15 node 3 size: 7842 MB node 3 free: 7723 MB node distances: node 0 1 2 3 0: 10 50 30 70 1: 50 10 70 30 2: 30 70 10 50 3: 70 30 50 10 And the cpumask_local_spread() for each node and offset traversing looks like this: node 0: 0 1 2 3 6 7 4 5 8 9 10 11 12 13 14 15 node 1: 4 5 8 9 10 11 12 13 14 15 0 1 2 3 6 7 node 2: 6 7 0 1 2 3 8 9 10 11 12 13 14 15 4 5 node 3: 8 9 10 11 12 13 14 15 4 5 6 7 0 1 2 3 Yury Norov (4): lib/find: introduce find_nth_and_andnot_bit cpumask: introduce cpumask_nth_and_andnot sched: add sched_numa_find_nth_cpu() cpumask: improve on cpumask_local_spread() locality include/linux/cpumask.h | 20 +++++++++++++++++++ include/linux/find.h | 33 +++++++++++++++++++++++++++++++ include/linux/topology.h | 8 ++++++++ kernel/sched/topology.c | 42 ++++++++++++++++++++++++++++++++++++++++ lib/cpumask.c | 12 ++---------- lib/find_bit.c | 9 +++++++++ 6 files changed, 114 insertions(+), 10 deletions(-) -- 2.34.1
