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perf evsel: Fix max perf_event_attr.precise_ip detection

Browse Source 
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: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/n/tip-dkvxxbeg7lu74155d4jhlmc9@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Jiri Olsa 2019-03-14 15:00:10 +01:00 committed by Arnaldo Carvalho de Melo
parent f3b4e06b3b
commit 4e8a5c1551
3 changed files with 59 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
tools/perf/util/evlist.c
View File

@ -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);

2
tools/perf/util/evlist.h
View File

@ -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);

72
tools/perf/util/evsel.c
View File

@ -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 @@ new_event:
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 @@ retry_sample_id:
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++) {
@ -1841,13 +1890,10 @@ retry_sample_id:
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],
group_fd, flags);
fd = perf_event_open(evsel, pid, cpus->map[cpu],
group_fd, flags);
FD(evsel, cpu, thread) = fd;