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| author | Stanislav Fomichev <sdf@google.com> | 2019-03-19 14:53:24 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2019-03-26 12:47:41 -0700 |
| commit | b4b6aa83433ea4675d4ba1be56774623db81f14f (patch) | |
| tree | 2e86ff15fa47e584d6c001355cbe3fe754d91543 | |
| parent | 0c4ea7f87abbdb56df616678bc23f10e51a0b4f8 (diff) | |
| download | linux-b4b6aa83433ea4675d4ba1be56774623db81f14f.tar.bz2 | |
selftests: bpf: don't depend on hardcoded perf sample_freq
When running stacktrace_build_id_nmi, try to query
kernel.perf_event_max_sample_rate sysctl and use it as a sample_freq.
If there was an error reading sysctl, fallback to 5000.
kernel.perf_event_max_sample_rate sysctl can drift and/or can be
adjusted by the perf tool, so assuming a fixed number might be
problematic on a long running machine.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c index 8a114bb1c379..1c1a2f75f3d8 100644 --- a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c +++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c @@ -1,13 +1,25 @@ // SPDX-License-Identifier: GPL-2.0 #include <test_progs.h> +static __u64 read_perf_max_sample_freq(void) +{ + __u64 sample_freq = 5000; /* fallback to 5000 on error */ + FILE *f; + + f = fopen("/proc/sys/kernel/perf_event_max_sample_rate", "r"); + if (f == NULL) + return sample_freq; + fscanf(f, "%llu", &sample_freq); + fclose(f); + return sample_freq; +} + void test_stacktrace_build_id_nmi(void) { int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd; const char *file = "./test_stacktrace_build_id.o"; int err, pmu_fd, prog_fd; struct perf_event_attr attr = { - .sample_freq = 5000, .freq = 1, .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_CPU_CYCLES, @@ -20,6 +32,8 @@ void test_stacktrace_build_id_nmi(void) int build_id_matches = 0; int retry = 1; + attr.sample_freq = read_perf_max_sample_freq(); + retry: err = bpf_prog_load(file, BPF_PROG_TYPE_PERF_EVENT, &obj, &prog_fd); if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno)) |