On 4/29/20 10:12 PM, Song Liu wrote:
On Apr 29, 2020, at 7:23 PM, Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote:
On Tue, Apr 28, 2020 at 11:47 PM Song Liu <songliubraving@xxxxxx> wrote:
Add test for BPF_ENABLE_STATS, which should enable run_time_ns stats.
~/selftests/bpf# ./test_progs -t enable_stats -v
test_enable_stats:PASS:skel_open_and_load 0 nsec
test_enable_stats:PASS:get_stats_fd 0 nsec
test_enable_stats:PASS:attach_raw_tp 0 nsec
test_enable_stats:PASS:get_prog_info 0 nsec
test_enable_stats:PASS:check_stats_enabled 0 nsec
test_enable_stats:PASS:check_run_cnt_valid 0 nsec
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Song Liu <songliubraving@xxxxxx>
---
.../selftests/bpf/prog_tests/enable_stats.c | 46 +++++++++++++++++++
.../selftests/bpf/progs/test_enable_stats.c | 18 ++++++++
2 files changed, 64 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/enable_stats.c
create mode 100644 tools/testing/selftests/bpf/progs/test_enable_stats.c
diff --git a/tools/testing/selftests/bpf/prog_tests/enable_stats.c b/tools/testing/selftests/bpf/prog_tests/enable_stats.c
new file mode 100644
index 000000000000..cb5e34dcfd42
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/enable_stats.c
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <sys/mman.h>
is this header used for anything?
Not really, will remove it.
+#include "test_enable_stats.skel.h"
+
+void test_enable_stats(void)
+{
[...]
+
+char _license[] SEC("license") = "GPL";
+
+static __u64 count;
this is actually very unreliable, because compiler might decide to
just remove this variable. It should be either `static volatile`, or
better use zero-initialized global variable:
__u64 count = 0;
Why would compile remove it? Is it because "static" or "no initialized?
Would "__u64 count;" work?
It is because of "static". This static variable has file scope and the
compiler COULD remove count+=1 since it does not have any other effect
other than incrementting itself and nobody uses it.
For "__u64 count = 0;", checkpatch.pl generates an error:
ERROR: do not initialise globals to 0
#92: FILE: tools/testing/selftests/bpf/progs/test_enable_stats.c:11:
+__u64 count = 0;
I think this is okay.
For llvm10, you have to use `__u64 count = 0`.
For llvm11, you can use "__u64 count", the compiler changed global
"common" variable treatment default from as a "common" var
to as a "bss" var.
In selftest, we have numerous cases for `__u64 count = 0` style
definitions and I recommend to use it as well since probably
quite some people uses llvm10 to compile/run selftests.
Thanks,
Song
