From: Xu Kuohai xukuohai@huawei.com
[ 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@huawei.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Acked-by: Yonghong Song yhs@fb.com Link: https://lore.kernel.org/bpf/20221110122128.105214-1-xukuohai@huawei.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/percpu_freelist.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-)
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++; } }