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Commit 4e8a5c15 authored by Jiri Olsa's avatar Jiri Olsa Committed by Arnaldo Carvalho de Melo
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perf evsel: Fix max perf_event_attr.precise_ip detection 



After a discussion with Andi, move the perf_event_attr.precise_ip
detection for maximum precise config (via :P modifier or for default
cycles event) to perf_evsel__open().

The current detection in perf_event_attr__set_max_precise_ip() is
tricky, because precise_ip config is specific for given event and it
currently checks only hw cycles.

We now check for valid precise_ip value right after failing
sys_perf_event_open() for specific event, before any of the
perf_event_attr fallback code gets executed.

This way we get the proper config in perf_event_attr together with
allowed precise_ip settings.

We can see that code activity with -vv, like:

  $ perf record -vv ls
  ...
  ------------------------------------------------------------
  perf_event_attr:
    size                             112
    { sample_period, sample_freq }   4000
    ...
    precise_ip                       3
    sample_id_all                    1
    exclude_guest                    1
    mmap2                            1
    comm_exec                        1
    ksymbol                          1
  ------------------------------------------------------------
  sys_perf_event_open: pid 9926  cpu 0  group_fd -1  flags 0x8
  sys_perf_event_open failed, error -95
  decreasing precise_ip by one (2)
  ------------------------------------------------------------
  perf_event_attr:
    size                             112
    { sample_period, sample_freq }   4000
    ...
    precise_ip                       2
    sample_id_all                    1
    exclude_guest                    1
    mmap2                            1
    comm_exec                        1
    ksymbol                          1
  ------------------------------------------------------------
  sys_perf_event_open: pid 9926  cpu 0  group_fd -1  flags 0x8 = 4
  ...

Suggested-by: default avatarAndi Kleen <ak@linux.intel.com>
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/n/tip-dkvxxbeg7lu74155d4jhlmc9@git.kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent f3b4e06b

tools/perf/util/evlist.c

+0 −29
Original line number Diff line number Diff line
@@ -231,35 +231,6 @@ void perf_evlist__set_leader(struct perf_evlist *evlist) 
	}

}



void perf_event_attr__set_max_precise_ip(struct perf_event_attr *pattr)

{

	struct perf_event_attr attr = {

		.type		= PERF_TYPE_HARDWARE,

		.config		= PERF_COUNT_HW_CPU_CYCLES,

		.exclude_kernel	= 1,

		.precise_ip	= 3,

	};



	event_attr_init(&attr);



	/*

	 * Unnamed union member, not supported as struct member named

	 * initializer in older compilers such as gcc 4.4.7

	 */

	attr.sample_period = 1;



	while (attr.precise_ip != 0) {

		int fd = sys_perf_event_open(&attr, 0, -1, -1, 0);

		if (fd != -1) {

			close(fd);

			break;

		}

		--attr.precise_ip;

	}



	pattr->precise_ip = attr.precise_ip;

}



int __perf_evlist__add_default(struct perf_evlist *evlist, bool precise)

{

	struct perf_evsel *evsel = perf_evsel__new_cycles(precise);

tools/perf/util/evlist.h

+0 −2
Original line number Diff line number Diff line
@@ -315,8 +315,6 @@ void perf_evlist__to_front(struct perf_evlist *evlist, 
void perf_evlist__set_tracking_event(struct perf_evlist *evlist,

				     struct perf_evsel *tracking_evsel);



void perf_event_attr__set_max_precise_ip(struct perf_event_attr *attr);



struct perf_evsel *

perf_evlist__find_evsel_by_str(struct perf_evlist *evlist, const char *str);

tools/perf/util/evsel.c

+59 −13
Original line number Diff line number Diff line
@@ -295,7 +295,6 @@ struct perf_evsel *perf_evsel__new_cycles(bool precise) 
	if (!precise)

		goto new_event;



	perf_event_attr__set_max_precise_ip(&attr);

	/*

	 * Now let the usual logic to set up the perf_event_attr defaults

	 * to kick in when we return and before perf_evsel__open() is called.
@@ -305,6 +304,8 @@ struct perf_evsel *perf_evsel__new_cycles(bool precise) 
	if (evsel == NULL)

		goto out;



	evsel->precise_max = true;



	/* use asprintf() because free(evsel) assumes name is allocated */

	if (asprintf(&evsel->name, "cycles%s%s%.*s",

		     (attr.precise_ip || attr.exclude_kernel) ? ":" : "",
@@ -1083,7 +1084,7 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts, 
	}



	if (evsel->precise_max)

		perf_event_attr__set_max_precise_ip(attr);

		attr->precise_ip = 3;



	if (opts->all_user) {

		attr->exclude_kernel = 1;
@@ -1749,6 +1750,59 @@ static bool ignore_missing_thread(struct perf_evsel *evsel, 
	return true;

}



static void display_attr(struct perf_event_attr *attr)

{

	if (verbose >= 2) {

		fprintf(stderr, "%.60s\n", graph_dotted_line);

		fprintf(stderr, "perf_event_attr:\n");

		perf_event_attr__fprintf(stderr, attr, __open_attr__fprintf, NULL);

		fprintf(stderr, "%.60s\n", graph_dotted_line);

	}

}



static int perf_event_open(struct perf_evsel *evsel,

			   pid_t pid, int cpu, int group_fd,

			   unsigned long flags)

{

	int precise_ip = evsel->attr.precise_ip;

	int fd;



	while (1) {

		pr_debug2("sys_perf_event_open: pid %d  cpu %d  group_fd %d  flags %#lx",

			  pid, cpu, group_fd, flags);



		fd = sys_perf_event_open(&evsel->attr, pid, cpu, group_fd, flags);

		if (fd >= 0)

			break;



		/*

		 * Do quick precise_ip fallback if:

		 *  - there is precise_ip set in perf_event_attr

		 *  - maximum precise is requested

		 *  - sys_perf_event_open failed with ENOTSUP error,

		 *    which is associated with wrong precise_ip

		 */

		if (!precise_ip || !evsel->precise_max || (errno != ENOTSUP))

			break;



		/*

		 * We tried all the precise_ip values, and it's

		 * still failing, so leave it to standard fallback.

		 */

		if (!evsel->attr.precise_ip) {

			evsel->attr.precise_ip = precise_ip;

			break;

		}



		pr_debug2("\nsys_perf_event_open failed, error %d\n", -ENOTSUP);

		evsel->attr.precise_ip--;

		pr_debug2("decreasing precise_ip by one (%d)\n", evsel->attr.precise_ip);

		display_attr(&evsel->attr);

	}



	return fd;

}



int perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,

		     struct thread_map *threads)

{
@@ -1824,12 +1878,7 @@ int perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus, 
	if (perf_missing_features.sample_id_all)

		evsel->attr.sample_id_all = 0;



	if (verbose >= 2) {

		fprintf(stderr, "%.60s\n", graph_dotted_line);

		fprintf(stderr, "perf_event_attr:\n");

		perf_event_attr__fprintf(stderr, &evsel->attr, __open_attr__fprintf, NULL);

		fprintf(stderr, "%.60s\n", graph_dotted_line);

	}

	display_attr(&evsel->attr);



	for (cpu = 0; cpu < cpus->nr; cpu++) {
@@ -1841,12 +1890,9 @@ int perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus, 


			group_fd = get_group_fd(evsel, cpu, thread);

retry_open:

			pr_debug2("sys_perf_event_open: pid %d  cpu %d  group_fd %d  flags %#lx",

				  pid, cpus->map[cpu], group_fd, flags);



			test_attr__ready();



			fd = sys_perf_event_open(&evsel->attr, pid, cpus->map[cpu],

			fd = perf_event_open(evsel, pid, cpus->map[cpu],

					     group_fd, flags);



			FD(evsel, cpu, thread) = fd;