| Message ID | 20230325185514.425745-1-yury.norov@gmail.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | sched/topology: add for_each_numa_cpu() macro | expand |
On Sat, Mar 25, 2023 at 11:55:06AM -0700, Yury Norov wrote: > for_each_cpu() is widely used in kernel, and it's beneficial to create > a NUMA-aware version of the macro. > > Recently added for_each_numa_hop_mask() works, but switching existing > codebase to it is not an easy process. > > This series adds for_each_numa_cpu(), which is designed to be similar to > the for_each_cpu(). It allows to convert existing code to NUMA-aware as > simple as adding a hop iterator variable and passing it inside new macro. > for_each_numa_cpu() takes care of the rest. > > At the moment, we have 2 users of NUMA-aware enumerators. One is > Melanox's in-tree driver, and another is Intel's in-review driver: > > https://lore.kernel.org/lkml/20230216145455.661709-1-pawel.chmielewski@intel.com/ Are there any more comments to the series? If not, I'll address those shared by Andy and send v2. Thanks, Yury
for_each_cpu() is widely used in kernel, and it's beneficial to create a NUMA-aware version of the macro. Recently added for_each_numa_hop_mask() works, but switching existing codebase to it is not an easy process. This series adds for_each_numa_cpu(), which is designed to be similar to the for_each_cpu(). It allows to convert existing code to NUMA-aware as simple as adding a hop iterator variable and passing it inside new macro. for_each_numa_cpu() takes care of the rest. At the moment, we have 2 users of NUMA-aware enumerators. One is Melanox's in-tree driver, and another is Intel's in-review driver: https://lore.kernel.org/lkml/20230216145455.661709-1-pawel.chmielewski@intel.com/ Both real-life examples follow the same pattern: for_each_numa_hop_mask(cpus, prev, node) { for_each_cpu_andnot(cpu, cpus, prev) { if (cnt++ == max_num) goto out; do_something(cpu); } prev = cpus; } With the new macro, it has a more standard look, like this: for_each_numa_cpu(cpu, hop, node, cpu_possible_mask) { if (cnt++ == max_num) break; do_something(cpu); } Straight conversion of existing for_each_cpu() codebase to NUMA-aware version with for_each_numa_hop_mask() is difficult because it doesn't take a user-provided cpu mask, and eventually ends up with open-coded double loop. With for_each_numa_cpu() it shouldn't be a brainteaser. Consider the NUMA-ignorant example: cpumask_t cpus = get_mask(); int cnt = 0, cpu; for_each_cpu(cpu, cpus) { if (cnt++ == max_num) break; do_something(cpu); } Converting it to NUMA-aware version would be as simple as: cpumask_t cpus = get_mask(); int node = get_node(); int cnt = 0, hop, cpu; for_each_numa_cpu(cpu, hop, node, cpus) { if (cnt++ == max_num) break; do_something(cpu); } The latter looks more verbose and avoids from open-coding that annoying double loop. Another advantage is that it works with a 'hop' parameter with the clear meaning of NUMA distance, and doesn't make people not familiar to enumerator internals bothering with current and previous masks machinery. Yury Norov (8): lib/find: add find_next_and_andnot_bit() sched/topology: introduce sched_numa_find_next_cpu() sched/topology: add for_each_numa_cpu() macro net: mlx5: switch comp_irqs_request() to using for_each_numa_cpu lib/cpumask: update comment to cpumask_local_spread() sched/topology: export sched_domains_numa_levels lib: add test for for_each_numa_{cpu,hop_mask}() sched: drop for_each_numa_hop_mask() drivers/net/ethernet/mellanox/mlx5/core/eq.c | 16 ++---- include/linux/find.h | 43 ++++++++++++++ include/linux/topology.h | 39 ++++++++----- kernel/sched/topology.c | 59 +++++++++++--------- lib/cpumask.c | 7 +-- lib/find_bit.c | 12 ++++ lib/test_bitmap.c | 16 ++++++ 7 files changed, 136 insertions(+), 56 deletions(-)