[PATCH bpf v2 2/2] selftests/bpf: add perf test for adjust_{head,meta}

[Jiayuan Chen <jiayuan.chen@linux.dev>]

We added a memset operation during the adjust operation, which may cause
performance issues.

Therefore, we added perf testing, and testing found that for common header
length operations, memset() operation increased the performance overhead
by 2ns, which is negligible for the net stack.

Before memset
./test_progs -a xdp_adjust_head_perf -v
run adjust head with size 6 cost 56 ns
run adjust head with size 20 cost 56 ns
run adjust head with size 40 cost 56 ns
run adjust head with size 200 cost 56 ns

After memset
./test_progs -a xdp_adjust_head_perf -v
run adjust head with size 6 cost 58 ns
run adjust head with size 20 cost 58 ns
run adjust head with size 40 cost 58 ns
run adjust head with size 200 cost 66 ns

Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
---
 .../selftests/bpf/prog_tests/xdp_perf.c       | 52 ++++++++++++++++---
 tools/testing/selftests/bpf/progs/xdp_dummy.c | 14 +++++
 2 files changed, 59 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_perf.c b/tools/testing/selftests/bpf/prog_tests/xdp_perf.c
index ec5369f247cb..1b4260c6e5d7 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_perf.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_perf.c
@@ -1,10 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <test_progs.h>
+#include <network_helpers.h>
+#include "xdp_dummy.skel.h"
 
 void test_xdp_perf(void)
 {
-	const char *file = "./xdp_dummy.bpf.o";
-	struct bpf_object *obj;
+	struct xdp_dummy *skel;
 	char in[128], out[128];
 	int err, prog_fd;
 	LIBBPF_OPTS(bpf_test_run_opts, topts,
@@ -15,14 +16,51 @@ void test_xdp_perf(void)
 		.repeat = 1000000,
 	);
 
-	err = bpf_prog_test_load(file, BPF_PROG_TYPE_XDP, &obj, &prog_fd);
-	if (CHECK_FAIL(err))
-		return;
-
+	skel = xdp_dummy__open_and_load();
+	prog_fd = bpf_program__fd(skel->progs.xdp_dummy_prog);
 	err = bpf_prog_test_run_opts(prog_fd, &topts);
 	ASSERT_OK(err, "test_run");
 	ASSERT_EQ(topts.retval, XDP_PASS, "test_run retval");
 	ASSERT_EQ(topts.data_size_out, 128, "test_run data_size_out");
 
-	bpf_object__close(obj);
+	xdp_dummy__destroy(skel);
+}
+
+void test_xdp_adjust_head_perf(void)
+{
+	struct xdp_dummy *skel;
+	int repeat = 9000000;
+	struct xdp_md ctx_in;
+	char data[100];
+	int err, prog_fd;
+	size_t test_header_size[] = {
+		ETH_ALEN,
+		sizeof(struct iphdr),
+		sizeof(struct ipv6hdr),
+		200,
+	};
+	DECLARE_LIBBPF_OPTS(bpf_test_run_opts, topts,
+			    .data_in = &data,
+			    .data_size_in = sizeof(data),
+			    .repeat = repeat,
+	);
+
+	topts.ctx_in = &ctx_in;
+	topts.ctx_size_in = sizeof(ctx_in);
+	memset(&ctx_in, 0, sizeof(ctx_in));
+	ctx_in.data_meta = 0;
+	ctx_in.data_end = ctx_in.data + sizeof(data);
+
+	skel = xdp_dummy__open_and_load();
+	prog_fd = bpf_program__fd(skel->progs.xdp_dummy_adjust_head);
+
+	for (int i = 0; i < ARRAY_SIZE(test_header_size); i++) {
+		skel->bss->head_size = test_header_size[i];
+		err = bpf_prog_test_run_opts(prog_fd, &topts);
+		ASSERT_OK(err, "test_run");
+		ASSERT_EQ(topts.retval, XDP_PASS, "test_run retval");
+		fprintf(stdout, "run adjust head with size %zd cost %d ns\n",
+			test_header_size[i], topts.duration);
+	}
+	xdp_dummy__destroy(skel);
 }
diff --git a/tools/testing/selftests/bpf/progs/xdp_dummy.c b/tools/testing/selftests/bpf/progs/xdp_dummy.c
index d988b2e0cee8..7bebedbbc949 100644
--- a/tools/testing/selftests/bpf/progs/xdp_dummy.c
+++ b/tools/testing/selftests/bpf/progs/xdp_dummy.c
@@ -4,10 +4,24 @@
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 
+int head_size;
+
 SEC("xdp")
 int xdp_dummy_prog(struct xdp_md *ctx)
 {
 	return XDP_PASS;
 }
 
+SEC("xdp")
+int xdp_dummy_adjust_head(struct xdp_md *ctx)
+{
+	if (bpf_xdp_adjust_head(ctx, -head_size))
+		return XDP_DROP;
+
+	if (bpf_xdp_adjust_head(ctx, head_size))
+		return XDP_DROP;
+
+	return XDP_PASS;
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.47.1