On Wed, Aug 23, 2023 at 4:00 AM Naveen N Rao [off-list ref] wrote:

Hi Kajol,

On Wed Aug 23, 2023 at 1:21 PM IST, Kajol Jain wrote:

quoted

Based on commit 7d54a4acd8c1 ("perf test: Skip watchpoint
tests if no watchpoints available"), hardware breakpoints
are not available for power9 platform and because of that
perf bench breakpoint run fails on power9 platform.
Add code to check for the return value of perf_event_open()
in breakpoint run and skip the perf bench breakpoint run,
if hardware breakpoints are not available.

Result on power9 system before patch changes:
[command]# perf bench breakpoint thread
perf_event_open: No such device

Result on power9 system after patch changes:
[command]# ./perf bench breakpoint thread
Skipping perf bench breakpoint thread: No hardware support

Reported-by: Disha Goel <redacted>
Signed-off-by: Kajol Jain <redacted>
---
 tools/perf/bench/breakpoint.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

Thanks for fixing this to not report an error. A minor nit below, but
otherwise:
Acked-by: Naveen N Rao <naveen@kernel.org>

quoted

diff --git a/tools/perf/bench/breakpoint.c b/tools/perf/bench/breakpoint.c
index 41385f89ffc7..dfd18f5db97d 100644
--- a/tools/perf/bench/breakpoint.c
+++ b/tools/perf/bench/breakpoint.c

@@ -47,6 +47,7 @@ struct breakpoint {
 static int breakpoint_setup(void *addr)
 {
      struct perf_event_attr attr = { .size = 0, };
+     int fd;

      attr.type = PERF_TYPE_BREAKPOINT;
      attr.size = sizeof(attr);

@@ -56,7 +57,12 @@ static int breakpoint_setup(void *addr)
      attr.bp_addr = (unsigned long)addr;
      attr.bp_type = HW_BREAKPOINT_RW;
      attr.bp_len = HW_BREAKPOINT_LEN_1;
-     return syscall(SYS_perf_event_open, &attr, 0, -1, -1, 0);
+     fd = syscall(SYS_perf_event_open, &attr, 0, -1, -1, 0);
+
+     if (fd < 0)
+             fd = -errno;
+
+     return fd;
 }

 static void *passive_thread(void *arg)

@@ -122,8 +128,14 @@ int bench_breakpoint_thread(int argc, const char **argv)

      for (i = 0; i < thread_params.nbreakpoints; i++) {
              breakpoints[i].fd = breakpoint_setup(&breakpoints[i].watched);
-             if (breakpoints[i].fd == -1)
+
+             if (breakpoints[i].fd < 0) {
+                     if (breakpoints[i].fd == -ENODEV) {
+                             printf("Skipping perf bench breakpoint thread: No hardware support\n");
+                             return 0;

Should we instead do 'exit(0)' here to stop further benchmarks? Perhaps:
  err(EXIT_SUCCESS, "Skipping perf bench breakpoint thread: No hardware support");

EXIT_SUCCESS looks weird, but should help document that this is not an
error.

In tools/perf/tests/tests.h is:

enum {
       TEST_OK   =  0,
       TEST_FAIL = -1,
       TEST_SKIP = -2,
};

So I think the EXIT_SUCCESS/0 should really be TEST_OK, but I think it
would clearer if these cases were TEST_SKIP.

Thanks,
Ian

quoted

+                     }
                      exit((perror("perf_event_open"), EXIT_FAILURE));
+             }
      }
      gettimeofday(&start, NULL);
      for (i = 0; i < thread_params.nparallel; i++) {

@@ -196,8 +208,14 @@ int bench_breakpoint_enable(int argc, const char **argv)
              exit(EXIT_FAILURE);
      }
      fd = breakpoint_setup(&watched);
-     if (fd == -1)
+
+     if (fd < 0) {
+             if (fd == -ENODEV) {
+                     printf("Skipping perf bench breakpoint enable: No hardware support\n");
+                     return 0;

Here too.

- Naveen

quoted

+             }
              exit((perror("perf_event_open"), EXIT_FAILURE));
+     }
      nthreads = enable_params.npassive + enable_params.nactive;
      threads = calloc(nthreads, sizeof(threads[0]));
      if (!threads)