selftests: bpf: don't depend on hardcoded perf sample_freq
authorStanislav Fomichev <sdf@google.com>
Tue, 19 Mar 2019 21:53:24 +0000 (14:53 -0700)
committerAlexei Starovoitov <ast@kernel.org>
Tue, 26 Mar 2019 19:47:41 +0000 (12:47 -0700)
commitb4b6aa83433ea4675d4ba1be56774623db81f14f
tree2e86ff15fa47e584d6c001355cbe3fe754d91543
parent0c4ea7f87abbdb56df616678bc23f10e51a0b4f8
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>
tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c