perf tests: Add test to check backward ring buffer

This test checks reading from backward ring buffer.

Test result:

  # ~/perf test 'ring buffer'
  45: Test backward reading from ring buffer                   : Ok

The test case is a while loop which calls prctl(PR_SET_NAME) multiple
times.  Each prctl should issue 2 events: one PERF_RECORD_SAMPLE, one
PERF_RECORD_COMM.

The first round creates a relative large ring buffer (256 pages). It can
afford all events. Read from it and check the count of each type of
events.

The second round creates a small ring buffer (1 page) and makes it
overwritable. Check the correctness of the buffer.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1462758471-89706-3-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
index 449fe97..66a2898 100644 (file)
--- a/tools/perf/tests/Build
+++ b/tools/perf/tests/Build
@@ -38,6 +38,7 @@ perf-y += cpumap.o
 perf-y += stat.o
 perf-y += event_update.o
 perf-y += event-times.o
+perf-y += backward-ring-buffer.o
 
 $(OUTPUT)tests/llvm-src-base.c: tests/bpf-script-example.c tests/Build
        $(call rule_mkdir)

diff --git a/tools/perf/tests/backward-ring-buffer.c b/tools/perf/tests/backward-ring-buffer.c
new file mode 100644 (file)
index 0000000..d9ba991
--- /dev/null
+++ b/tools/perf/tests/backward-ring-buffer.c
@@ -0,0 +1,151 @@
+/*
+ * Test backward bit in event attribute, read ring buffer from end to
+ * beginning
+ */
+
+#include <perf.h>
+#include <evlist.h>
+#include <sys/prctl.h>
+#include "tests.h"
+#include "debug.h"
+
+#define NR_ITERS 111
+
+static void testcase(void)
+{
+       int i;
+
+       for (i = 0; i < NR_ITERS; i++) {
+               char proc_name[10];
+
+               snprintf(proc_name, sizeof(proc_name), "p:%d\n", i);
+               prctl(PR_SET_NAME, proc_name);
+       }
+}
+
+static int count_samples(struct perf_evlist *evlist, int *sample_count,
+                        int *comm_count)
+{
+       int i;
+
+       for (i = 0; i < evlist->nr_mmaps; i++) {
+               union perf_event *event;
+
+               perf_evlist__mmap_read_catchup(evlist, i);
+               while ((event = perf_evlist__mmap_read_backward(evlist, i)) != NULL) {
+                       const u32 type = event->header.type;
+
+                       switch (type) {
+                       case PERF_RECORD_SAMPLE:
+                               (*sample_count)++;
+                               break;
+                       case PERF_RECORD_COMM:
+                               (*comm_count)++;
+                               break;
+                       default:
+                               pr_err("Unexpected record of type %d\n", type);
+                               return TEST_FAIL;
+                       }
+               }
+       }
+       return TEST_OK;
+}
+
+static int do_test(struct perf_evlist *evlist, int mmap_pages,
+                  int *sample_count, int *comm_count)
+{
+       int err;
+       char sbuf[STRERR_BUFSIZE];
+
+       err = perf_evlist__mmap(evlist, mmap_pages, true);
+       if (err < 0) {
+               pr_debug("perf_evlist__mmap: %s\n",
+                        strerror_r(errno, sbuf, sizeof(sbuf)));
+               return TEST_FAIL;
+       }
+
+       perf_evlist__enable(evlist);
+       testcase();
+       perf_evlist__disable(evlist);
+
+       err = count_samples(evlist, sample_count, comm_count);
+       perf_evlist__munmap(evlist);
+       return err;
+}
+
+
+int test__backward_ring_buffer(int subtest __maybe_unused)
+{
+       int ret = TEST_SKIP, err, sample_count = 0, comm_count = 0;
+       char pid[16], sbuf[STRERR_BUFSIZE];
+       struct perf_evlist *evlist;
+       struct perf_evsel *evsel __maybe_unused;
+       struct parse_events_error parse_error;
+       struct record_opts opts = {
+               .target = {
+                       .uid = UINT_MAX,
+                       .uses_mmap = true,
+               },
+               .freq         = 0,
+               .mmap_pages   = 256,
+               .default_interval = 1,
+       };
+
+       snprintf(pid, sizeof(pid), "%d", getpid());
+       pid[sizeof(pid) - 1] = '\0';
+       opts.target.tid = opts.target.pid = pid;
+
+       evlist = perf_evlist__new();
+       if (!evlist) {
+               pr_debug("No ehough memory to create evlist\n");
+               return TEST_FAIL;
+       }
+
+       err = perf_evlist__create_maps(evlist, &opts.target);
+       if (err < 0) {
+               pr_debug("Not enough memory to create thread/cpu maps\n");
+               goto out_delete_evlist;
+       }
+
+       bzero(&parse_error, sizeof(parse_error));
+       err = parse_events(evlist, "syscalls:sys_enter_prctl", &parse_error);
+       if (err) {
+               pr_debug("Failed to parse tracepoint event, try use root\n");
+               ret = TEST_SKIP;
+               goto out_delete_evlist;
+       }
+
+       perf_evlist__config(evlist, &opts, NULL);
+
+       /* Set backward bit, ring buffer should be writing from end */
+       evlist__for_each(evlist, evsel)
+               evsel->attr.write_backward = 1;
+
+       err = perf_evlist__open(evlist);
+       if (err < 0) {
+               pr_debug("perf_evlist__open: %s\n",
+                        strerror_r(errno, sbuf, sizeof(sbuf)));
+               goto out_delete_evlist;
+       }
+
+       ret = TEST_FAIL;
+       err = do_test(evlist, opts.mmap_pages, &sample_count,
+                     &comm_count);
+       if (err != TEST_OK)
+               goto out_delete_evlist;
+
+       if ((sample_count != NR_ITERS) || (comm_count != NR_ITERS)) {
+               pr_err("Unexpected counter: sample_count=%d, comm_count=%d\n",
+                      sample_count, comm_count);
+               goto out_delete_evlist;
+       }
+
+       err = do_test(evlist, 1, &sample_count, &comm_count);
+       if (err != TEST_OK)
+               goto out_delete_evlist;
+
+       ret = TEST_OK;
+out_delete_evlist:
+       perf_evlist__delete(evlist);
+       return ret;
+}

diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index 93c4670..0e95c20 100644 (file)
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -207,6 +207,10 @@ static struct test generic_tests[] = {
                .desc = "Test events times",
                .func = test__event_times,
        },
+       {
+               .desc = "Test backward reading from ring buffer",
+               .func = test__backward_ring_buffer,
+       },
        {
                .func = NULL,
        },

diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
index 0fc9469..c57e72c 100644 (file)
--- a/tools/perf/tests/tests.h
+++ b/tools/perf/tests/tests.h
@@ -86,6 +86,7 @@ int test__synthesize_stat(int subtest);
 int test__synthesize_stat_round(int subtest);
 int test__event_update(int subtest);
 int test__event_times(int subtest);
+int test__backward_ring_buffer(int subtest);
 
 #if defined(__arm__) || defined(__aarch64__)
 #ifdef HAVE_DWARF_UNWIND_SUPPORT