selftests/bpf/benchs: Add overwrite mode bench for rb-libbpf

Add overwrite mode bench for ring buffer.

For reference, below are bench numbers collected from x86_64 and arm64.

- x86_64 (AMD EPYC 9654)

  Ringbuf, multi-producer contention, overwrite mode
  ==================================================
  rb-libbpf nr_prod 1  14.970 ± 0.012M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 2  14.064 ± 0.007M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 3  7.493 ± 0.003M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 4  6.575 ± 0.001M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 8  3.696 ± 0.011M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 12 2.612 ± 0.012M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 16 2.335 ± 0.005M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 20 2.079 ± 0.005M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 24 1.965 ± 0.004M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 28 1.846 ± 0.004M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 32 1.790 ± 0.002M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 36 1.735 ± 0.002M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 40 1.701 ± 0.002M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 44 1.669 ± 0.001M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 48 1.749 ± 0.001M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 52 1.709 ± 0.001M/s (drops 0.000 ± 0.000M/s)

- arm64 (HiSilicon Kunpeng 920)

  Ringbuf, multi-producer contention, overwrite mode
  ==================================================
  rb-libbpf nr_prod 1  10.319 ± 0.231M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 2  9.219 ± 0.006M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 3  6.699 ± 0.013M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 4  4.608 ± 0.001M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 8  3.905 ± 0.001M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 12 3.282 ± 0.004M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 16 3.182 ± 0.008M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 20 3.029 ± 0.006M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 24 3.116 ± 0.004M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 28 2.869 ± 0.005M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 32 3.075 ± 0.010M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 36 2.795 ± 0.003M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 40 2.947 ± 0.005M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 44 2.748 ± 0.006M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 48 2.767 ± 0.003M/s (drops 0.000 ± 0.000M/s)
  rb-libbpf nr_prod 52 2.858 ± 0.002M/s (drops 0.000 ± 0.000M/s)

Signed-off-by: Xu Kuohai <[email protected]>

Author: Xu Kuohai

tools/testing/selftests/bpf/benchs/bench_ringbufs.c

@@ -19,6 +19,7 @@ static struct {
 	int ringbuf_sz; /* per-ringbuf, in bytes */
 	bool ringbuf_use_output; /* use slower output API */
 	int perfbuf_sz; /* per-CPU size, in pages */
+	bool overwrite_mode;
 } args = {
 	.back2back = false,
 	.batch_cnt = 500,
@@ -27,6 +28,7 @@ static struct {
 	.ringbuf_sz = 512 * 1024,
 	.ringbuf_use_output = false,
 	.perfbuf_sz = 128,
+	.overwrite_mode = false,
 };
 
 enum {
@@ -35,6 +37,7 @@ enum {
 	ARG_RB_BATCH_CNT = 2002,
 	ARG_RB_SAMPLED = 2003,
 	ARG_RB_SAMPLE_RATE = 2004,
+	ARG_RB_OVERWRITE = 2005,
 };
 
 static const struct argp_option opts[] = {
@@ -43,6 +46,7 @@ static const struct argp_option opts[] = {
 	{ "rb-batch-cnt", ARG_RB_BATCH_CNT, "CNT", 0, "Set BPF-side record batch count"},
 	{ "rb-sampled", ARG_RB_SAMPLED, NULL, 0, "Notification sampling"},
 	{ "rb-sample-rate", ARG_RB_SAMPLE_RATE, "RATE", 0, "Notification sample rate"},
+	{ "rb-overwrite", ARG_RB_OVERWRITE, NULL, 0, "overwrite mode"},
 	{},
 };
 
@@ -72,6 +76,9 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
 			argp_usage(state);
 		}
 		break;
+	case ARG_RB_OVERWRITE:
+		args.overwrite_mode = true;
+		break;
 	default:
 		return ARGP_ERR_UNKNOWN;
 	}
@@ -104,6 +111,11 @@ static void bufs_validate(void)
 		fprintf(stderr, "back-to-back mode makes sense only for single-producer case!\n");
 		exit(1);
 	}
+
+	if (args.overwrite_mode && strcmp(env.bench_name, "rb-libbpf") != 0) {
+		fprintf(stderr, "rb-overwrite mode only supports rb-libbpf!\n");
+		exit(1);
+	}
 }
 
 static void *bufs_sample_producer(void *input)
@@ -134,6 +146,8 @@ static void ringbuf_libbpf_measure(struct bench_res *res)
 
 static struct ringbuf_bench *ringbuf_setup_skeleton(void)
 {
+	__u32 flags;
+	struct bpf_map *ringbuf;
 	struct ringbuf_bench *skel;
 
 	setup_libbpf();
@@ -151,7 +165,13 @@ static struct ringbuf_bench *ringbuf_setup_skeleton(void)
 		/* record data + header take 16 bytes */
 		skel->rodata->wakeup_data_size = args.sample_rate * 16;
 
-	bpf_map__set_max_entries(skel->maps.ringbuf, args.ringbuf_sz);
+	ringbuf = skel->maps.ringbuf;
+	if (args.overwrite_mode) {
+		flags = bpf_map__map_flags(ringbuf) | BPF_F_OVERWRITE;
+		bpf_map__set_map_flags(ringbuf,  flags);
+	}
+
+	bpf_map__set_max_entries(ringbuf, args.ringbuf_sz);
 
 	if (ringbuf_bench__load(skel)) {
 		fprintf(stderr, "failed to load skeleton\n");

tools/testing/selftests/bpf/benchs/run_bench_ringbufs.sh

@@ -49,3 +49,7 @@ for b in 1 2 3 4 8 12 16 20 24 28 32 36 40 44 48 52; do
 	summarize "rb-libbpf nr_prod $b" "$($RUN_RB_BENCH -p$b --rb-batch-cnt 50 rb-libbpf)"
 done
 
+header "Ringbuf, multi-producer contention, overwrite mode"
+for b in 1 2 3 4 8 12 16 20 24 28 32 36 40 44 48 52; do
+	summarize "rb-libbpf nr_prod $b" "$($RUN_RB_BENCH -p$b --rb-overwrite --rb-batch-cnt 50 rb-libbpf)"
+done