[PATCH v1 23/25] perf pmu: Be lazy about loading event info files from sysfs

From: Ian Rogers
Date: Wed Aug 23 2023 - 04:22:37 EST

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Event info is only needed when an event is parsed or when merging data
from an json and sysfs event. Be lazy in its loading to reduce file
accesses.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
tools/perf/util/pmu.c | 128 +++++++++++++++++++++++++++---------------
1 file changed, 83 insertions(+), 45 deletions(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index b4ba4f7f5e18..c547fe607f9f 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -58,6 +58,11 @@ struct perf_pmu_alias {
struct list_head terms;
/** @list: List element of struct perf_pmu aliases. */
struct list_head list;
+ /**
+ * @pmu_name: The name copied from the json struct pmu_event. This can
+ * differ from the PMU name as it won't have suffixes.
+ */
+ char *pmu_name;
/** @unit: Units for the event, such as bytes or cache lines. */
char unit[UNIT_MAX_LEN+1];
/** @scale: Value to scale read counter values by. */
@@ -79,11 +84,10 @@ struct perf_pmu_alias {
* default.
*/
bool deprecated;
- /**
- * @pmu_name: The name copied from the json struct pmu_event. This can
- * differ from the PMU name as it won't have suffixes.
- */
- char *pmu_name;
+ /** @from_sysfs: Was the alias from sysfs or a json event? */
+ bool from_sysfs;
+ /** @info_loaded: Have the scale, unit and other values been read from disk? */
+ bool info_loaded;
};

/**
@@ -276,17 +280,21 @@ int perf_pmu__convert_scale(const char *scale, char **end, double *sval)
return ret;
}

-static int perf_pmu__parse_scale(struct perf_pmu_alias *alias, int dirfd, const char *name)
+static int perf_pmu__parse_scale(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
{
struct stat st;
ssize_t sret;
+ size_t len;
char scale[128];
int fd, ret = -1;
char path[PATH_MAX];

- scnprintf(path, PATH_MAX, "%s.scale", name);
+ len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
+ if (!len)
+ return 0;
+ scnprintf(path + len, sizeof(path) - len, "%s/%s.scale", pmu->name, alias->name);

- fd = openat(dirfd, path, O_RDONLY);
+ fd = open(path, O_RDONLY);
if (fd == -1)
return -1;

@@ -308,15 +316,20 @@ static int perf_pmu__parse_scale(struct perf_pmu_alias *alias, int dirfd, const
return ret;
}

-static int perf_pmu__parse_unit(struct perf_pmu_alias *alias, int dirfd, const char *name)
+static int perf_pmu__parse_unit(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
{
char path[PATH_MAX];
+ size_t len;
ssize_t sret;
int fd;

- scnprintf(path, PATH_MAX, "%s.unit", name);

- fd = openat(dirfd, path, O_RDONLY);
+ len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
+ if (!len)
+ return 0;
+ scnprintf(path + len, sizeof(path) - len, "%s/%s.unit", pmu->name, alias->name);
+
+ fd = open(path, O_RDONLY);
if (fd == -1)
return -1;

@@ -339,14 +352,18 @@ static int perf_pmu__parse_unit(struct perf_pmu_alias *alias, int dirfd, const c
}

static int
-perf_pmu__parse_per_pkg(struct perf_pmu_alias *alias, int dirfd, const char *name)
+perf_pmu__parse_per_pkg(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
{
char path[PATH_MAX];
+ size_t len;
int fd;

- scnprintf(path, PATH_MAX, "%s.per-pkg", name);
+ len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
+ if (!len)
+ return 0;
+ scnprintf(path + len, sizeof(path) - len, "%s/%s.per-pkg", pmu->name, alias->name);

- fd = openat(dirfd, path, O_RDONLY);
+ fd = open(path, O_RDONLY);
if (fd == -1)
return -1;

@@ -356,15 +373,18 @@ perf_pmu__parse_per_pkg(struct perf_pmu_alias *alias, int dirfd, const char *nam
return 0;
}

-static int perf_pmu__parse_snapshot(struct perf_pmu_alias *alias,
- int dirfd, const char *name)
+static int perf_pmu__parse_snapshot(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
{
char path[PATH_MAX];
+ size_t len;
int fd;

- scnprintf(path, PATH_MAX, "%s.snapshot", name);
+ len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
+ if (!len)
+ return 0;
+ scnprintf(path + len, sizeof(path) - len, "%s/%s.snapshot", pmu->name, alias->name);

- fd = openat(dirfd, path, O_RDONLY);
+ fd = open(path, O_RDONLY);
if (fd == -1)
return -1;

@@ -425,32 +445,52 @@ static bool assign_str(const char *name, const char *field, char **old_str,
return true;
}

+static void read_alias_info(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
+{
+ if (!alias->from_sysfs || alias->info_loaded)
+ return;
+
+ /*
+ * load unit name and scale if available
+ */
+ perf_pmu__parse_unit(pmu, alias);
+ perf_pmu__parse_scale(pmu, alias);
+ perf_pmu__parse_per_pkg(pmu, alias);
+ perf_pmu__parse_snapshot(pmu, alias);
+}
+
+struct update_alias_data {
+ struct perf_pmu *pmu;
+ struct perf_pmu_alias *alias;
+};
+
static int update_alias(const struct pmu_event *pe,
const struct pmu_events_table *table __maybe_unused,
void *vdata)
{
- struct perf_pmu_alias *alias = vdata;
+ struct update_alias_data *data = vdata;
int ret = 0;

- assign_str(pe->name, "desc", &alias->desc, pe->desc);
- assign_str(pe->name, "long_desc", &alias->long_desc, pe->long_desc);
- assign_str(pe->name, "topic", &alias->topic, pe->topic);
- alias->per_pkg = pe->perpkg;
- if (assign_str(pe->name, "value", &alias->str, pe->event)) {
- parse_events_terms__purge(&alias->terms);
- ret = parse_events_terms(&alias->terms, pe->event, /*input=*/NULL);
+ read_alias_info(data->pmu, data->alias);
+ assign_str(pe->name, "desc", &data->alias->desc, pe->desc);
+ assign_str(pe->name, "long_desc", &data->alias->long_desc, pe->long_desc);
+ assign_str(pe->name, "topic", &data->alias->topic, pe->topic);
+ data->alias->per_pkg = pe->perpkg;
+ if (assign_str(pe->name, "value", &data->alias->str, pe->event)) {
+ parse_events_terms__purge(&data->alias->terms);
+ ret = parse_events_terms(&data->alias->terms, pe->event, /*input=*/NULL);
}
if (!ret && pe->unit) {
char *unit;

- ret = perf_pmu__convert_scale(pe->unit, &unit, &alias->scale);
+ ret = perf_pmu__convert_scale(pe->unit, &unit, &data->alias->scale);
if (!ret)
- snprintf(alias->unit, sizeof(alias->unit), "%s", unit);
+ snprintf(data->alias->unit, sizeof(data->alias->unit), "%s", unit);
}
return ret;
}

-static int perf_pmu__new_alias(struct perf_pmu *pmu, int dirfd, const char *name,
+static int perf_pmu__new_alias(struct perf_pmu *pmu, const char *name,
const char *desc, const char *val, FILE *val_fd,
const struct pmu_event *pe)
{
@@ -494,16 +534,6 @@ static int perf_pmu__new_alias(struct perf_pmu *pmu, int dirfd, const char *name
}

alias->name = strdup(name);
- if (dirfd >= 0) {
- /*
- * load unit name and scale if available
- */
- perf_pmu__parse_unit(alias, dirfd, name);
- perf_pmu__parse_scale(alias, dirfd, name);
- perf_pmu__parse_per_pkg(alias, dirfd, name);
- perf_pmu__parse_snapshot(alias, dirfd, name);
- }
-
alias->desc = desc ? strdup(desc) : NULL;
alias->long_desc = long_desc ? strdup(long_desc) :
desc ? strdup(desc) : NULL;
@@ -518,9 +548,15 @@ static int perf_pmu__new_alias(struct perf_pmu *pmu, int dirfd, const char *name
}
if (!pe) {
/* Update an event from sysfs with json data. */
+ struct update_alias_data data = {
+ .pmu = pmu,
+ .alias = alias,
+ };
+
+ alias->from_sysfs = true;
if (pmu->events_table) {
if (pmu_events_table__find_event(pmu->events_table, pmu, name,
- update_alias, alias) == 0)
+ update_alias, &data) == 0)
pmu->loaded_json_aliases++;
}
}
@@ -608,7 +644,7 @@ static int pmu_aliases_parse(struct perf_pmu *pmu, int dirfd)
continue;
}

- if (perf_pmu__new_alias(pmu, dirfd, name, /*desc=*/ NULL,
+ if (perf_pmu__new_alias(pmu, name, /*desc=*/ NULL,
/*val=*/ NULL, file, /*pe=*/ NULL) < 0)
pr_debug("Cannot set up %s\n", name);
fclose(file);
@@ -861,7 +897,7 @@ static int pmu_add_cpu_aliases_map_callback(const struct pmu_event *pe,
{
struct perf_pmu *pmu = vdata;

- perf_pmu__new_alias(pmu, -1, pe->name, pe->desc, pe->event, /*val_fd=*/ NULL, pe);
+ perf_pmu__new_alias(pmu, pe->name, pe->desc, pe->event, /*val_fd=*/ NULL, pe);
return 0;
}

@@ -897,7 +933,7 @@ static int pmu_add_sys_aliases_iter_fn(const struct pmu_event *pe,

if (!strcmp(pmu->id, pe->compat) &&
pmu_uncore_alias_match(pe->pmu, pmu->name)) {
- perf_pmu__new_alias(pmu, -1,
+ perf_pmu__new_alias(pmu,
pe->name,
pe->desc,
pe->event,
@@ -1413,11 +1449,13 @@ static struct perf_pmu_alias *pmu_find_alias(struct perf_pmu *pmu,
}

-static int check_info_data(struct perf_pmu_alias *alias,
+static int check_info_data(struct perf_pmu *pmu,
+ struct perf_pmu_alias *alias,
struct perf_pmu_info *info,
struct parse_events_error *err,
int column)
{
+ read_alias_info(pmu, alias);
/*
* Only one term in event definition can
* define unit, scale and snapshot, fail
@@ -1487,7 +1525,7 @@ int perf_pmu__check_alias(struct perf_pmu *pmu, struct list_head *head_terms,
return ret;
}

- ret = check_info_data(alias, info, err, term->err_term);
+ ret = check_info_data(pmu, alias, info, err, term->err_term);
if (ret)
return ret;

--
2.42.0.rc1.204.g551eb34607-goog

Next message: Krzysztof Kozlowski: "[PATCH] dt-bindings: display: advantech,idk-2121wr: reference common panel"
Previous message: Ian Rogers: "[PATCH v1 22/25] perf pmu: Scan type early to fail an invalid PMU quickly"
In reply to: Ian Rogers: "[PATCH v1 22/25] perf pmu: Scan type early to fail an invalid PMU quickly"
Next in thread: Ian Rogers: "Re: [PATCH v1 00/25] Lazily load PMU data"
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