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Subject[PATCH 8/9] sample/bpf: sockex1: user percpu array map
Date
It is demonstrated the expensive atomic operations can
be removed in eBPF prog.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
samples/bpf/sockex1_kern.c | 7 ++++---
samples/bpf/sockex1_user.c | 20 ++++++++++++++++----
2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/samples/bpf/sockex1_kern.c b/samples/bpf/sockex1_kern.c
index ed18e9a..400518a 100644
--- a/samples/bpf/sockex1_kern.c
+++ b/samples/bpf/sockex1_kern.c
@@ -5,7 +5,7 @@
#include "bpf_helpers.h"

struct bpf_map_def SEC("maps") my_map = {
- .type = BPF_MAP_TYPE_ARRAY,
+ .type = BPF_MAP_TYPE_ARRAY_PERCPU,
.key_size = sizeof(u32),
.value_size = sizeof(long),
.max_entries = 256,
@@ -16,13 +16,14 @@ int bpf_prog1(struct __sk_buff *skb)
{
int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
long *value;
+ unsigned cpu = bpf_get_smp_processor_id();

if (skb->pkt_type != PACKET_OUTGOING)
return 0;

- value = bpf_map_lookup_elem(&my_map, &index);
+ value = bpf_map_lookup_elem_percpu(&my_map, &index, cpu);
if (value)
- __sync_fetch_and_add(value, skb->len);
+ *value += skb->len;

return 0;
}
diff --git a/samples/bpf/sockex1_user.c b/samples/bpf/sockex1_user.c
index 678ce46..8572e81 100644
--- a/samples/bpf/sockex1_user.c
+++ b/samples/bpf/sockex1_user.c
@@ -6,6 +6,14 @@
#include <unistd.h>
#include <arpa/inet.h>

+static int handle_one_cpu(unsigned cpu, void *val_cpu, void *val)
+{
+ long long *cnt = val;
+
+ *cnt += *(long *)val_cpu;
+ return 0;
+}
+
int main(int ac, char **argv)
{
char filename[256];
@@ -28,17 +36,21 @@ int main(int ac, char **argv)
(void) f;

for (i = 0; i < 5; i++) {
- long long tcp_cnt, udp_cnt, icmp_cnt;
+ long cnt_percpu;
+ long long tcp_cnt = 0, udp_cnt = 0, icmp_cnt = 0;
int key;

key = IPPROTO_TCP;
- assert(bpf_lookup_elem(map_fd[0], &key, &tcp_cnt) == 0);
+ assert(bpf_lookup_elem_allcpu(map_fd[0], &key,
+ &cnt_percpu, &tcp_cnt, handle_one_cpu) == 0);

key = IPPROTO_UDP;
- assert(bpf_lookup_elem(map_fd[0], &key, &udp_cnt) == 0);
+ assert(bpf_lookup_elem_allcpu(map_fd[0], &key,
+ &cnt_percpu, &udp_cnt, handle_one_cpu) == 0);

key = IPPROTO_ICMP;
- assert(bpf_lookup_elem(map_fd[0], &key, &icmp_cnt) == 0);
+ assert(bpf_lookup_elem_allcpu(map_fd[0], &key,
+ &cnt_percpu, &icmp_cnt, handle_one_cpu) == 0);

printf("TCP %lld UDP %lld ICMP %lld bytes\n",
tcp_cnt, udp_cnt, icmp_cnt);
--
1.9.1
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