[PATCH bpf-next v4 4/4] selftests/bpf: add usage example for cpu cycles kfuncs

Vadim Fedorenko
2024-11-07T21:12:56Z

The selftest provides an example of how to measure the latency of bpf
kfunc/helper call in cycles and nanoseconds.

Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
---
.../bpf/prog_tests/test_cpu_cycles.c | 35 +++++++++++++++++++
.../selftests/bpf/progs/test_cpu_cycles.c | 25 +++++++++++++
2 files changed, 60 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/test_cpu_cycles.c
create mode 100644 tools/testing/selftests/bpf/progs/test_cpu_cycles.c

diff --git a/tools/testing/selftests/bpf/prog_tests/test_cpu_cycles.c b/tools/testing/selftests/bpf/prog_tests/test_cpu_cycles.c
new file mode 100644
index 000000000000..d7f3b66594b3
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/test_cpu_cycles.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Inc. */
+
+#include <test_progs.h>
+#include "test_cpu_cycles.skel.h"
+
+static void cpu_cycles(void)
+{
+ LIBBPF_OPTS(bpf_test_run_opts, opts);
+ struct test_cpu_cycles *skel;
+ int err, pfd;
+
+ skel = test_cpu_cycles__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "test_cpu_cycles open and load"))
+ return;
+
+ pfd = bpf_program__fd(skel->progs.bpf_cpu_cycles);
+ if (!ASSERT_GT(pfd, 0, "test_cpu_cycles fd"))
+ goto fail;
+
+ err = bpf_prog_test_run_opts(pfd, &opts);
+ if (!ASSERT_OK(err, "test_cpu_cycles test run"))
+ goto fail;
+
+ ASSERT_NEQ(skel->bss->cycles, 0, "test_cpu_cycles 0 cycles");
+ ASSERT_NEQ(skel->bss->ns, 0, "test_cpu_cycles 0 ns");
+fail:
+ test_cpu_cycles__destroy(skel);
+}
+
+void test_cpu_cycles(void)
+{
+ if (test__start_subtest("cpu_cycles"))
+ cpu_cycles();
+}
diff --git a/tools/testing/selftests/bpf/progs/test_cpu_cycles.c b/tools/testing/selftests/bpf/progs/test_cpu_cycles.c
new file mode 100644
index 000000000000..48762f07ad7f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_cpu_cycles.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Inc. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+extern u64 bpf_cpu_cycles_to_ns(u64 cycles) __weak __ksym;
+extern u64 bpf_get_cpu_cycles(void) __weak __ksym;
+
+__u64 cycles, ns;
+
+SEC("syscall")
+int bpf_cpu_cycles(void)
+{
+ struct bpf_pidns_info pidns;
+ __u64 start;
+
+ start = bpf_get_cpu_cycles();
+ bpf_get_ns_current_pid_tgid(0, 0, &pidns, sizeof(struct bpf_pidns_info));
+ cycles = bpf_get_cpu_cycles() - start;
+ ns = bpf_cpu_cycles_to_ns(cycles);
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.43.5