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Message-Id: <20221108142207.4079521-1-xukuohai@huaweicloud.com>
Date: Tue, 8 Nov 2022 09:22:07 -0500
From: Xu Kuohai <xukuohai@...weicloud.com>
To: bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>
Subject: [PATCH bpf-next v2] bpf: Initialize same number of free nodes for each pcpu_freelist
From: Xu Kuohai <xukuohai@...wei.com>
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, if CPU 0 is the current cpu, 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.
Signed-off-by: Xu Kuohai <xukuohai@...wei.com>
Acked-by: Yonghong Song <yhs@...com>
---
v2: Update commit message and add Yonghong's ack
---
kernel/bpf/percpu_freelist.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/bpf/percpu_freelist.c b/kernel/bpf/percpu_freelist.c
index b6e7f5c5b9ab..89e84f7381cc 100644
--- a/kernel/bpf/percpu_freelist.c
+++ b/kernel/bpf/percpu_freelist.c
@@ -100,12 +100,15 @@ 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;
+ int i, cpu, pcpu_entries, remain_entries;
+
+ pcpu_entries = nr_elems / num_possible_cpus();
+ remain_entries = nr_elems % num_possible_cpus();
- pcpu_entries = nr_elems / num_possible_cpus() + 1;
i = 0;
for_each_possible_cpu(cpu) {
+ int j = i + pcpu_entries + (remain_entries-- > 0 ? 1 : 0);
again:
head = per_cpu_ptr(s->freelist, cpu);
/* No locking required as this is not visible yet. */
@@ -114,7 +117,7 @@ void pcpu_freelist_populate(struct pcpu_freelist *s, void *buf, u32 elem_size,
buf += elem_size;
if (i == nr_elems)
break;
- if (i % pcpu_entries)
+ if (i < j)
goto again;
}
}
--
2.30.2
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