[tip: perf/core] perf pmu: Add support for PMU capabilities

From: tip-bot2 for Kan Liang
Date: Wed Apr 22 2020 - 08:22:42 EST

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The following commit has been merged into the perf/core branch of tip:

Commit-ID: 9fbc61f832ebf432326a90e28184dade05ee34a8
Gitweb: https://git.kernel.org/tip/9fbc61f832ebf432326a90e28184dade05ee34a8
Author: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
AuthorDate: Thu, 19 Mar 2020 13:25:01 -07:00
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitterDate: Sat, 18 Apr 2020 09:05:00 -03:00

perf pmu: Add support for PMU capabilities

The PMU capabilities information, which is located at
/sys/bus/event_source/devices/<dev>/caps, is required by perf tool. For
example, the max LBR information is required to stitch LBR call stack.

Add perf_pmu__caps_parse() to parse the PMU capabilities information.
The information is stored in a list.

The following patch will store the capabilities information in perf
header.

Committer notes:

Here's an example of such directories and its files in an i5 7th gen
machine:

[root@seventh ~]# ls -lad /sys/bus/event_source/devices/*/caps
drwxr-xr-x. 2 root root 0 Apr 14 13:33 /sys/bus/event_source/devices/cpu/caps
drwxr-xr-x. 2 root root 0 Apr 14 13:33 /sys/bus/event_source/devices/intel_pt/caps
[root@seventh ~]# ls -la /sys/bus/event_source/devices/intel_pt/caps
total 0
drwxr-xr-x. 2 root root 0 Apr 14 13:33 .
drwxr-xr-x. 5 root root 0 Apr 14 13:12 ..
-r--r--r--. 1 root root 4096 Apr 16 13:10 cr3_filtering
-r--r--r--. 1 root root 4096 Apr 16 11:42 cycle_thresholds
-r--r--r--. 1 root root 4096 Apr 16 13:10 ip_filtering
-r--r--r--. 1 root root 4096 Apr 16 13:10 max_subleaf
-r--r--r--. 1 root root 4096 Apr 14 13:33 mtc
-r--r--r--. 1 root root 4096 Apr 14 13:33 mtc_periods
-r--r--r--. 1 root root 4096 Apr 16 13:10 num_address_ranges
-r--r--r--. 1 root root 4096 Apr 16 13:10 output_subsys
-r--r--r--. 1 root root 4096 Apr 16 13:10 payloads_lip
-r--r--r--. 1 root root 4096 Apr 16 13:10 power_event_trace
-r--r--r--. 1 root root 4096 Apr 14 13:33 psb_cyc
-r--r--r--. 1 root root 4096 Apr 14 13:33 psb_periods
-r--r--r--. 1 root root 4096 Apr 16 13:10 ptwrite
-r--r--r--. 1 root root 4096 Apr 16 13:10 single_range_output
-r--r--r--. 1 root root 4096 Apr 16 12:03 topa_multiple_entries
-r--r--r--. 1 root root 4096 Apr 16 13:10 topa_output
[root@seventh ~]# cat /sys/bus/event_source/devices/intel_pt/caps/topa_output
1
[root@seventh ~]# cat /sys/bus/event_source/devices/intel_pt/caps/topa_multiple_entries
1
[root@seventh ~]# cat /sys/bus/event_source/devices/intel_pt/caps/mtc
1
[root@seventh ~]# cat /sys/bus/event_source/devices/intel_pt/caps/power_event_trace
0
[root@seventh ~]#

[root@seventh ~]# ls -la /sys/bus/event_source/devices/cpu/caps/
total 0
drwxr-xr-x. 2 root root 0 Apr 14 13:33 .
drwxr-xr-x. 6 root root 0 Apr 14 13:12 ..
-r--r--r--. 1 root root 4096 Apr 16 13:10 branches
-r--r--r--. 1 root root 4096 Apr 14 13:33 max_precise
-r--r--r--. 1 root root 4096 Apr 16 13:10 pmu_name
[root@seventh ~]# cat /sys/bus/event_source/devices/cpu/caps/max_precise
3
[root@seventh ~]# cat /sys/bus/event_source/devices/cpu/caps/branches
32
[root@seventh ~]# cat /sys/bus/event_source/devices/cpu/caps/pmu_name
skylake
[root@seventh ~]#

Wow, first time I've heard about
/sys/bus/event_source/devices/cpu/caps/max_precise, I think I'll use it!
:-)

Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Pavel Gerasimov <pavel.gerasimov@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Vitaly Slobodskoy <vitaly.slobodskoy@xxxxxxxxx>
Link: http://lore.kernel.org/lkml/20200319202517.23423-2-kan.liang@xxxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/util/pmu.c | 82 ++++++++++++++++++++++++++++++++++++++++++-
tools/perf/util/pmu.h | 9 +++++-
2 files changed, 91 insertions(+)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index bc912a8..d9f89ed 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -850,6 +850,7 @@ static struct perf_pmu *pmu_lookup(const char *name)

INIT_LIST_HEAD(&pmu->format);
INIT_LIST_HEAD(&pmu->aliases);
+ INIT_LIST_HEAD(&pmu->caps);
list_splice(&format, &pmu->format);
list_splice(&aliases, &pmu->aliases);
list_add_tail(&pmu->list, &pmus);
@@ -1594,3 +1595,84 @@ int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt,
va_end(args);
return ret;
}
+
+static int perf_pmu__new_caps(struct list_head *list, char *name, char *value)
+{
+ struct perf_pmu_caps *caps = zalloc(sizeof(*caps));
+
+ if (!caps)
+ return -ENOMEM;
+
+ caps->name = strdup(name);
+ if (!caps->name)
+ goto free_caps;
+ caps->value = strndup(value, strlen(value) - 1);
+ if (!caps->value)
+ goto free_name;
+ list_add_tail(&caps->list, list);
+ return 0;
+
+free_name:
+ zfree(caps->name);
+free_caps:
+ free(caps);
+
+ return -ENOMEM;
+}
+
+/*
+ * Reading/parsing the given pmu capabilities, which should be located at:
+ * /sys/bus/event_source/devices/<dev>/caps as sysfs group attributes.
+ * Return the number of capabilities
+ */
+int perf_pmu__caps_parse(struct perf_pmu *pmu)
+{
+ struct stat st;
+ char caps_path[PATH_MAX];
+ const char *sysfs = sysfs__mountpoint();
+ DIR *caps_dir;
+ struct dirent *evt_ent;
+ int nr_caps = 0;
+
+ if (!sysfs)
+ return -1;
+
+ snprintf(caps_path, PATH_MAX,
+ "%s" EVENT_SOURCE_DEVICE_PATH "%s/caps", sysfs, pmu->name);
+
+ if (stat(caps_path, &st) < 0)
+ return 0; /* no error if caps does not exist */
+
+ caps_dir = opendir(caps_path);
+ if (!caps_dir)
+ return -EINVAL;
+
+ while ((evt_ent = readdir(caps_dir)) != NULL) {
+ char path[PATH_MAX + NAME_MAX + 1];
+ char *name = evt_ent->d_name;
+ char value[128];
+ FILE *file;
+
+ if (!strcmp(name, ".") || !strcmp(name, ".."))
+ continue;
+
+ snprintf(path, sizeof(path), "%s/%s", caps_path, name);
+
+ file = fopen(path, "r");
+ if (!file)
+ continue;
+
+ if (!fgets(value, sizeof(value), file) ||
+ (perf_pmu__new_caps(&pmu->caps, name, value) < 0)) {
+ fclose(file);
+ continue;
+ }
+
+ nr_caps++;
+ fclose(file);
+ }
+
+ closedir(caps_dir);
+
+ return nr_caps;
+}
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 5fb3f16..1edd214 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -22,6 +22,12 @@ enum {

struct perf_event_attr;

+struct perf_pmu_caps {
+ char *name;
+ char *value;
+ struct list_head list;
+};
+
struct perf_pmu {
char *name;
__u32 type;
@@ -33,6 +39,7 @@ struct perf_pmu {
struct perf_cpu_map *cpus;
struct list_head format; /* HEAD struct perf_pmu_format -> list */
struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
+ struct list_head caps; /* HEAD struct perf_pmu_caps -> list */
struct list_head list; /* ELEM */
};

@@ -107,4 +114,6 @@ bool pmu_uncore_alias_match(const char *pmu_name, const char *name);

int perf_pmu__convert_scale(const char *scale, char **end, double *sval);

+int perf_pmu__caps_parse(struct perf_pmu *pmu);
+
#endif /* __PMU_H */

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