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Subject[RFC PATCHv3] perf tools: add event grouping capability to "perf stat"
Date
Add the ability to create multiple event groups, each with their own leader
using the existing "-e <event>[,<event> ...] [-e <event>[,<event>]]"
syntax. Each additional -e switch creates a new group, and each event
listed within a -e switch is within that group.

Changes since v1:
- Because of a flub, v2 did not contain the changes I had intended to make,
and instead, v2 had the same patch contents as v1.
- When perf stat is not supplied any events on the command line, put
each default event in its own group.

Signed-off-by: Corey Ashford <cjashfor@linux.vnet.ibm.com>
---
tools/perf/Documentation/perf-stat.txt | 12 +++++++++---
tools/perf/builtin-stat.c | 16 ++++++++++++++--
tools/perf/util/parse-events.c | 4 ++++
tools/perf/util/parse-events.h | 1 +
4 files changed, 28 insertions(+), 5 deletions(-)
diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 4b3a2d4..d522ebd 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -8,8 +8,8 @@ perf-stat - Run a command and gather performance counter statistics
SYNOPSIS
--------
[verse]
-'perf stat' [-e <EVENT> | --event=EVENT] [-S] [-a] <command>
-'perf stat' [-e <EVENT> | --event=EVENT] [-S] [-a] -- <command> [<options>]
+'perf stat' [-e <EVENT>[,<EVENT>...] | --event=<EVENT>[,<EVENT>...]] [-S] [-a] <command>
+'perf stat' [-e <EVENT>[,<EVENT>...] | --event=<EVENT>[,<EVENT>...]] [-S] [-a] -- <command> [<options>]

DESCRIPTION
-----------
@@ -28,7 +28,13 @@ OPTIONS
Select the PMU event. Selection can be a symbolic event name
(use 'perf list' to list all events) or a raw PMU
event (eventsel+umask) in the form of rNNN where NNN is a
- hexadecimal event descriptor.
+ hexadecimal event descriptor. As shown, multiple events can be
+ separated by commas in each -e/--event switch. Each additional
+ -e/--event switch creates a new event group. Grouped events are
+ scheduled onto the PMU hardware at the same time, which is
+ important to know when the PMU is overscheduled. A good example of
+ this is measuring CPI where both instructions and cycles events
+ need to be scheduled simultaneously to get an accurate estimate.

-i::
--no-inherit::
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 8b9afa6..8a17e9b 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -162,8 +162,12 @@ static int create_perf_stat_counter(int counter, bool *perm_err)
int cpu;

for (cpu = 0; cpu < nr_cpus; cpu++) {
+ if (counter == grp_leaders[counter])
+ /* first counter in the group is the leader */
+ fd[cpu][grp_leaders[counter]][0] = -1;
fd[cpu][counter][0] = sys_perf_event_open(attr,
- -1, cpumap[cpu], -1, 0);
+ -1, cpumap[cpu],
+ fd[cpu][grp_leaders[counter]][0], 0);
if (fd[cpu][counter][0] < 0) {
if (errno == EPERM || errno == EACCES)
*perm_err = true;
@@ -180,8 +184,12 @@ static int create_perf_stat_counter(int counter, bool *perm_err)
attr->enable_on_exec = 1;
}
for (thread = 0; thread < thread_num; thread++) {
+ if (counter == grp_leaders[counter])
+ /* first counter in the group is the leader */
+ fd[0][grp_leaders[counter]][thread] = -1;
fd[0][counter][thread] = sys_perf_event_open(attr,
- all_tids[thread], -1, -1, 0);
+ all_tids[thread], -1,
+ fd[0][grp_leaders[counter]][thread], 0);
if (fd[0][counter][thread] < 0) {
if (errno == EPERM || errno == EACCES)
*perm_err = true;
@@ -576,6 +584,10 @@ int cmd_stat(int argc, const char **argv, const char *prefix __used)
if (!null_run && !nr_counters) {
memcpy(attrs, default_attrs, sizeof(default_attrs));
nr_counters = ARRAY_SIZE(default_attrs);
+ for (i = 0; i < nr_counters; i++) {
+ /* each default event should be in its own group */
+ grp_leaders[i] = i;
+ }
}

if (system_wide)
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 4af5bd5..eeecb2a 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -12,6 +12,7 @@

int nr_counters;

+int grp_leaders[MAX_COUNTERS];
struct perf_event_attr attrs[MAX_COUNTERS];
char *filters[MAX_COUNTERS];

@@ -804,11 +805,13 @@ int parse_events(const struct option *opt __used, const char *str, int unset __u
{
struct perf_event_attr attr;
enum event_result ret;
+ int grp_leader;

if (strchr(str, ':'))
if (store_event_type(str) < 0)
return -1;

+ grp_leader = nr_counters;
for (;;) {
if (nr_counters == MAX_COUNTERS)
return -1;
@@ -822,6 +825,7 @@ int parse_events(const struct option *opt __used, const char *str, int unset __u
return -1;

if (ret != EVT_HANDLED_ALL) {
+ grp_leaders[nr_counters] = grp_leader;
attrs[nr_counters] = attr;
nr_counters++;
}
diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
index fc4ab3f..d820f42 100644
--- a/tools/perf/util/parse-events.h
+++ b/tools/perf/util/parse-events.h
@@ -17,6 +17,7 @@ extern bool have_tracepoints(struct perf_event_attr *pattrs, int nb_events);

extern int nr_counters;

+extern int grp_leaders[MAX_COUNTERS];
extern struct perf_event_attr attrs[MAX_COUNTERS];
extern char *filters[MAX_COUNTERS];

--
1.7.0.4


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