Re: [PATCH v3 2/2] perf tests: Add test to check backward ring buffer

[Arnaldo Carvalho de Melo]

Em Mon, May 09, 2016 at 01:47:51AM +0000, Wang Nan escreveu:
> This test checks reading from backward ring buffer.
> 
> Test result:
> 
>  # ~/perf test 'ring buffer'
>  45: Test backward reading from ring buffer                   : Ok

Thanks, applied and also I added a patch to show that bit when using
-vv, i.e.:

      # perf test -vv back
      45: Test backward reading from ring buffer                   :
      --- start ---
      <SNIP>
      ------------------------------------------------------------
      perf_event_attr:
        type                             2
        size                             112
        config                           0x98
        { sample_period, sample_freq }   1
        sample_type                      IP|TID|TIME|CPU|PERIOD|RAW
        disabled                         1
        mmap                             1
        comm                             1
        task                             1
        sample_id_all                    1
        exclude_guest                    1
        mmap2                            1
        comm_exec                        1
        write_backward                   1
      ------------------------------------------------------------
      <SNIP>
 
> 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@xxxxxxxxxx>
> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Zefan Li <lizefan@xxxxxxxxxx>
> Cc: pi3orama@xxxxxxx
> ---
>  tools/perf/tests/Build                  |   1 +
>  tools/perf/tests/backward-ring-buffer.c | 151 ++++++++++++++++++++++++++++++++
>  tools/perf/tests/builtin-test.c         |   4 +
>  tools/perf/tests/tests.h                |   1 +
>  4 files changed, 157 insertions(+)
>  create mode 100644 tools/perf/tests/backward-ring-buffer.c
> 
> diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
> index 449fe97..66a2898 100644
> --- 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
> 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
> --- a/tools/perf/tests/builtin-test.c
> +++ b/tools/perf/tests/builtin-test.c
> @@ -208,6 +208,10 @@ static struct test generic_tests[] = {
>  		.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
> --- 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
> -- 
> 1.8.3.4