skb_attempt_defer_free() only queues skbs on the current CPU's node (numa_node_id() of a running CPU), which is always online, so the flush loop never needs to visit nodes that are merely possible. for_each_node() walks node_possible_map. On machines where the possible map is much larger than the online map -- e.g. a POWER10 LPAR with 32 possible but 1 online node -- the flush loop touches 31 cold, always-empty per-node lists on every softirq pass, showing up as skb_defer_free_flush() and _find_next_bit() overhead. Use for_each_online_node() to iterate only node_online_map. Loopback UDP throughput in a QEMU guest with 32 possible / 1 online nodes (bench_udp, 8 senders, 6 interleaved runs) improves by ~5%. Fixes: 5628f3fe3b16 ("net: add NUMA awareness to skb_attempt_defer_free()") Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202512112119.5b9829a-lkp@intel.com Signed-off-by: Kris Pan --- net/core/dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index 290e0f099e6bf..b528b6a986fcf 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6907,7 +6907,7 @@ static void skb_defer_free_flush(void) struct skb_defer_node *sdn; int node; - for_each_node(node) { + for_each_online_node(node) { sdn = this_cpu_ptr(net_hotdata.skb_defer_nodes) + node; if (llist_empty(&sdn->defer_list)) -- 2.43.0