在 2022/6/1 下午5:53, Alexei Starovoitov 写道:
On Wed, Jun 1, 2022 at 10:42 AM Feng zhou <zhoufeng.zf@xxxxxxxxxxxxx> wrote:
+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __type(key, u32);
+ __type(value, u64);
+ __uint(max_entries, MAX_ENTRIES);
+} hash_map_bench SEC(".maps");
+
+u64 __attribute__((__aligned__(256))) percpu_time[256];
aligned 256 ?
What is the point?
I didn't think too much about it here, just referenced it from
tools/testing/selftests/bpf/progs/bloom_filter_bench.c
+u64 nr_loops;
+
+static int loop_update_callback(__u32 index, u32 *key)
+{
+ u64 init_val = 1;
+
+ bpf_map_update_elem(&hash_map_bench, key, &init_val, BPF_ANY);
+ return 0;
+}
+
+SEC("fentry/" SYS_PREFIX "sys_getpgid")
+int benchmark(void *ctx)
+{
+ u32 key = bpf_get_prandom_u32() % MAX_ENTRIES + MAX_ENTRIES;
What is the point of random ?
just key = MAX_ENTRIES would be the same, no?
or key = -1 ?
If all threads on different cpu trigger sys_getpgid and lookup the same
key, it will cause
"ret = htab_lock_bucket(htab, b, hash, &flags); "
the lock competition here is fierce, and unnecessary overhead is
introduced,
and I don't want it to interfere with the test.
+ u32 cpu = bpf_get_smp_processor_id();
+ u64 start_time = bpf_ktime_get_ns();
+
+ bpf_loop(nr_loops, loop_update_callback, &key, 0);
+ percpu_time[cpu & 255] = bpf_ktime_get_ns() - start_time;
+ return 0;
+}
--
2.20.1
