Thanks for the review Andrii!
> On Feb 19, 2022, at 8:39 PM, Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Fri, Feb 18, 2022 at 4:30 PM Mykola Lysenko <mykolal@xxxxxx> wrote:
>>
>> In send_signal, replace sleep with dummy cpu intensive computation
>> to increase probability of child process being scheduled. Add few
>> more asserts.
>>
>> In find_vma, reduce sample_freq as higher values may be rejected in
>> some qemu setups, remove usleep and increase length of cpu intensive
>> computation.
>>
>> In bpf_cookie, perf_link and perf_branches, reduce sample_freq as
>> higher values may be rejected in some qemu setups
>>
>> Signed-off-by: Mykola Lysenko <mykolal@xxxxxx>
>> ---
>> .../testing/selftests/bpf/prog_tests/bpf_cookie.c | 2 +-
>> tools/testing/selftests/bpf/prog_tests/find_vma.c | 5 ++---
>> .../selftests/bpf/prog_tests/perf_branches.c | 4 ++--
>> tools/testing/selftests/bpf/prog_tests/perf_link.c | 2 +-
>> .../testing/selftests/bpf/prog_tests/send_signal.c | 14 ++++++++++----
>> 5 files changed, 16 insertions(+), 11 deletions(-)
>>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
>> index cd10df6cd0fc..0612e79a9281 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
>> @@ -199,7 +199,7 @@ static void pe_subtest(struct test_bpf_cookie *skel)
>> attr.type = PERF_TYPE_SOFTWARE;
>> attr.config = PERF_COUNT_SW_CPU_CLOCK;
>> attr.freq = 1;
>> - attr.sample_freq = 4000;
>> + attr.sample_freq = 1000;
>> pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
>> if (!ASSERT_GE(pfd, 0, "perf_fd"))
>> goto cleanup;
>> diff --git a/tools/testing/selftests/bpf/prog_tests/find_vma.c b/tools/testing/selftests/bpf/prog_tests/find_vma.c
>> index b74b3c0c555a..acc41223a112 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/find_vma.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/find_vma.c
>> @@ -30,7 +30,7 @@ static int open_pe(void)
>> attr.type = PERF_TYPE_HARDWARE;
>> attr.config = PERF_COUNT_HW_CPU_CYCLES;
>> attr.freq = 1;
>> - attr.sample_freq = 4000;
>> + attr.sample_freq = 1000;
>> pfd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, PERF_FLAG_FD_CLOEXEC);
>>
>> return pfd >= 0 ? pfd : -errno;
>> @@ -57,7 +57,7 @@ static void test_find_vma_pe(struct find_vma *skel)
>> if (!ASSERT_OK_PTR(link, "attach_perf_event"))
>> goto cleanup;
>>
>> - for (i = 0; i < 1000000; ++i)
>> + for (i = 0; i < 1000000000; ++i)
>
> 1bln seems excessive... maybe 10mln would be enough?
See explanation for send_signal test case below
>
>> ++j;
>>
>> test_and_reset_skel(skel, -EBUSY /* in nmi, irq_work is busy */);
>
> [...]
>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal.c b/tools/testing/selftests/bpf/prog_tests/send_signal.c
>> index 776916b61c40..841217bd1df6 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/send_signal.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/send_signal.c
>> @@ -4,11 +4,12 @@
>> #include <sys/resource.h>
>> #include "test_send_signal_kern.skel.h"
>>
>> -int sigusr1_received = 0;
>> +int sigusr1_received;
>> +volatile int volatile_variable;
>
> please make them static
sure
>
>>
>> static void sigusr1_handler(int signum)
>> {
>> - sigusr1_received++;
>> + sigusr1_received = 1;
>> }
>>
>> static void test_send_signal_common(struct perf_event_attr *attr,
>> @@ -42,7 +43,9 @@ static void test_send_signal_common(struct perf_event_attr *attr,
>> int old_prio;
>>
>> /* install signal handler and notify parent */
>> + errno = 0;
>> signal(SIGUSR1, sigusr1_handler);
>> + ASSERT_OK(errno, "signal");
>
> just ASSERT_OK(signal(...), "signal");
I am fine to merge signal and ASSERT lines, but will substitute with condition "signal(SIGUSR1, sigusr1_handler) != SIG_ERR”, sounds good?
>
>>
>> close(pipe_c2p[0]); /* close read */
>> close(pipe_p2c[1]); /* close write */
>> @@ -63,9 +66,12 @@ static void test_send_signal_common(struct perf_event_attr *attr,
>> ASSERT_EQ(read(pipe_p2c[0], buf, 1), 1, "pipe_read");
>>
>> /* wait a little for signal handler */
>> - sleep(1);
>> + for (int i = 0; i < 1000000000; i++)
>
> same about 1bln
With 10mln and 100 test runs I got 86 failures
100mln - 63 failures
1bln - 0 failures on 100 runs
Now, there is performance concern for this test. Running
time sudo ./test_progs -t send_signal/send_signal_nmi_thread
With 1bln takes ~4s
100mln - 1s.
Unchanged test with sleep(1); takes ~2s.
On the other hand 300mln runs ~2s, and only fails 1 time per 100 runs. As 300mln does not regress performance comparing to the current “sleep(1)” implementation, I propose to go with it. What do you think?
>
>> + volatile_variable++;
>>
>> buf[0] = sigusr1_received ? '2' : '0';
>> + ASSERT_EQ(sigusr1_received, 1, "sigusr1_received");
>> +
>> ASSERT_EQ(write(pipe_c2p[1], buf, 1), 1, "pipe_write");
>>
>> /* wait for parent notification and exit */
>> @@ -110,9 +116,9 @@ static void test_send_signal_common(struct perf_event_attr *attr,
>> ASSERT_EQ(read(pipe_c2p[0], buf, 1), 1, "pipe_read");
>>
>> /* trigger the bpf send_signal */
>> + skel->bss->signal_thread = signal_thread;
>> skel->bss->pid = pid;
>> skel->bss->sig = SIGUSR1;
>> - skel->bss->signal_thread = signal_thread;
>>
>> /* notify child that bpf program can send_signal now */
>> ASSERT_EQ(write(pipe_p2c[1], buf, 1), 1, "pipe_write");
>> --
>> 2.30.2
