Re: [PATCHv2 5/8] perf tools: Get precise_ip from the pmu config

Jiri Olsa
2019-03-14T14:01:30Z

On Thu, Mar 07, 2019 at 08:51:23AM -0800, Andi Kleen wrote:
> On Thu, Mar 07, 2019 at 04:35:00PM +0100, Jiri Olsa wrote:
> > On Tue, Mar 05, 2019 at 08:40:17AM -0800, Andi Kleen wrote:
> > > On Tue, Mar 05, 2019 at 05:28:54PM +0100, Jiri Olsa wrote:
> > > > On Tue, Mar 05, 2019 at 08:13:19AM -0800, Andi Kleen wrote:
> > > > > On Tue, Mar 05, 2019 at 04:25:33PM +0100, Jiri Olsa wrote:
> > > > > > Getting precise_ip field from the perf_pmu::max_precise
> > > > > > config read from sysfs. If it's not available falling
> > > > > > back to current detection function.
> > > > >
> > > > > max_precise depends on the event. This won't work for all
> > > > > events. For example only instructions and cycles support
> > > > > ppp
> > > >
> > > > I'm getting precise_ip=3 on mem-* events as well, that's why I
> > > > was fixing this.. now it's not working for any event
> > >
> > > I don't think it means anything for mem-*
> > >
> > > There's some support for it on Goldmont plus for other events,
> > > but it doesn't support mem-*. On big core it's only
> > > for instructions and cycles, all implemented with the same
> > > event. All other PEBS events only have two levels
> > > switching between the two IPs.
> >
> > ok, so how about this, it's the change I posted merged with the patch
>
> Still seems like a hack. Even though I don't know of a case that
> would break now. But it would be better to have the precise probing
> in the open retry loop, instead of trying to reinvent it here.

how about something like below?

jirka

---
tools/perf/util/evlist.c | 29 ----------------
tools/perf/util/evlist.h | 2 --
tools/perf/util/evsel.c | 73 +++++++++++++++++++++++++++++++++-------
3 files changed, 60 insertions(+), 44 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index ed20f4379956..3a243c249c29 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -230,35 +230,6 @@ 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);
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 744906dd4887..cb15e3366eba 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -303,8 +303,6 @@ 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);

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 3bbf73e979c0..7cd70f99201a 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -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 +1750,60 @@ 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 requested:
+ * - there is some precise_ip
+ * - maximum precise is requested
+ * - we failed with ENOTSUP error, which is
+ * associated with wrong precise_ip config
+ */
+ 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 fallabck.
+ */
+ 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 +1879,7 @@ 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++) {

@@ -1841,13 +1891,10 @@ 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],
- group_fd, flags);
+ fd = perf_event_open(evsel, pid, cpus->map[cpu],
+ group_fd, flags);

FD(evsel, cpu, thread) = fd;

--
2.17.2