This is a note to let you know that I've just added the patch titled bpf: Initialize same number of free nodes for each pcpu_freelist to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bpf-initialize-same-number-of-free-nodes-for-each-pc.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 1223d4692d437bef78b58a20e13851452f582821 Author: Xu Kuohai <xukuohai@xxxxxxxxxx> Date: Thu Nov 10 07:21:28 2022 -0500 bpf: Initialize same number of free nodes for each pcpu_freelist [ Upstream commit 4b45cd81f737d79d0fbfc0d320a1e518e7f0bbf0 ] pcpu_freelist_populate() initializes nr_elems / num_possible_cpus() + 1 free nodes for some CPUs, and then possibly one CPU with fewer nodes, followed by remaining cpus with 0 nodes. For example, when nr_elems == 256 and num_possible_cpus() == 32, CPU 0~27 each gets 9 free nodes, CPU 28 gets 4 free nodes, CPU 29~31 get 0 free nodes, while in fact each CPU should get 8 nodes equally. This patch initializes nr_elems / num_possible_cpus() free nodes for each CPU firstly, then allocates the remaining free nodes by one for each CPU until no free nodes left. Fixes: e19494edab82 ("bpf: introduce percpu_freelist") Signed-off-by: Xu Kuohai <xukuohai@xxxxxxxxxx> Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> Acked-by: Yonghong Song <yhs@xxxxxx> Link: https://lore.kernel.org/bpf/20221110122128.105214-1-xukuohai@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/kernel/bpf/percpu_freelist.c b/kernel/bpf/percpu_freelist.c index 3d897de89061..bbab8bb4b2fd 100644 --- a/kernel/bpf/percpu_freelist.c +++ b/kernel/bpf/percpu_freelist.c @@ -102,22 +102,21 @@ void pcpu_freelist_populate(struct pcpu_freelist *s, void *buf, u32 elem_size, u32 nr_elems) { struct pcpu_freelist_head *head; - int i, cpu, pcpu_entries; + unsigned int cpu, cpu_idx, i, j, n, m; - pcpu_entries = nr_elems / num_possible_cpus() + 1; - i = 0; + n = nr_elems / num_possible_cpus(); + m = nr_elems % num_possible_cpus(); + cpu_idx = 0; for_each_possible_cpu(cpu) { -again: head = per_cpu_ptr(s->freelist, cpu); - /* No locking required as this is not visible yet. */ - pcpu_freelist_push_node(head, buf); - i++; - buf += elem_size; - if (i == nr_elems) - break; - if (i % pcpu_entries) - goto again; + j = n + (cpu_idx < m ? 1 : 0); + for (i = 0; i < j; i++) { + /* No locking required as this is not visible yet. */ + pcpu_freelist_push_node(head, buf); + buf += elem_size; + } + cpu_idx++; } }