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Message-ID: <20240612133911.3447625-4-ben.gainey@arm.com>
Date: Wed, 12 Jun 2024 14:39:10 +0100
From: Ben Gainey <ben.gainey@....com>
To: peterz@...radead.org,
mingo@...hat.com,
acme@...nel.org,
namhyung@...nel.org
Cc: james.clark@....com,
mark.rutland@....com,
alexander.shishkin@...ux.intel.com,
jolsa@...nel.org,
irogers@...gle.com,
adrian.hunter@...el.com,
linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org,
Ben Gainey <ben.gainey@....com>
Subject: [PATCH v8 3/4] tools/perf: Correctly calculate sample period for inherited SAMPLE_READ values
Sample period calculation in deliver_sample_value is updated to
calculate the per-thread period delta for events that are inherit +
PERF_SAMPLE_READ. When the sampling event has this configuration, the
read_format.id is used with the tid from the sample to lookup the
storage of the previously accumulated counter total before calculating
the delta. All existing valid configurations where read_format.value
represents some global value continue to use just the read_format.id to
locate the storage of the previously accumulated total.
perf_sample_id is modified to support tracking per-thread
values, along with the existing global per-id values. In the
per-thread case, values are stored in a hash by tid within the
perf_sample_id, and are dynamically allocated as the number is not known
ahead of time.
Signed-off-by: Ben Gainey <ben.gainey@....com>
---
tools/lib/perf/evsel.c | 48 +++++++++++++++++++
tools/lib/perf/include/internal/evsel.h | 63 ++++++++++++++++++++++++-
tools/perf/util/session.c | 25 ++++++----
3 files changed, 126 insertions(+), 10 deletions(-)
diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
index c07160953224..abdae2f9498b 100644
--- a/tools/lib/perf/evsel.c
+++ b/tools/lib/perf/evsel.c
@@ -5,6 +5,7 @@
#include <perf/evsel.h>
#include <perf/cpumap.h>
#include <perf/threadmap.h>
+#include <linux/hash.h>
#include <linux/list.h>
#include <internal/evsel.h>
#include <linux/zalloc.h>
@@ -23,6 +24,7 @@ void perf_evsel__init(struct perf_evsel *evsel, struct perf_event_attr *attr,
int idx)
{
INIT_LIST_HEAD(&evsel->node);
+ INIT_LIST_HEAD(&evsel->per_stream_periods);
evsel->attr = *attr;
evsel->idx = idx;
evsel->leader = evsel;
@@ -531,10 +533,56 @@ int perf_evsel__alloc_id(struct perf_evsel *evsel, int ncpus, int nthreads)
void perf_evsel__free_id(struct perf_evsel *evsel)
{
+ struct perf_sample_id_period *pos, *n;
+
xyarray__delete(evsel->sample_id);
evsel->sample_id = NULL;
zfree(&evsel->id);
evsel->ids = 0;
+
+ perf_evsel_for_each_per_thread_period_safe(evsel, n, pos) {
+ list_del_init(&pos->node);
+ free(pos);
+ }
+}
+
+bool perf_evsel__attr_has_per_thread_sample_period(struct perf_evsel *evsel)
+{
+ return (evsel->attr.sample_type & PERF_SAMPLE_READ)
+ && (evsel->attr.sample_type & PERF_SAMPLE_TID)
+ && evsel->attr.inherit;
+}
+
+u64 *perf_sample_id__get_period_storage(struct perf_sample_id *sid, u32 tid, bool per_thread)
+{
+ struct hlist_head *head;
+ struct perf_sample_id_period *res;
+ int hash;
+
+ if (!per_thread)
+ return &sid->period;
+
+ hash = hash_32(tid, PERF_SAMPLE_ID__HLIST_BITS);
+ head = &sid->periods[hash];
+
+ hlist_for_each_entry(res, head, hnode)
+ if (res->tid == tid)
+ return &res->period;
+
+ if (sid->evsel == NULL)
+ return NULL;
+
+ res = zalloc(sizeof(struct perf_sample_id_period));
+ if (res == NULL)
+ return NULL;
+
+ INIT_LIST_HEAD(&res->node);
+ res->tid = tid;
+
+ list_add_tail(&res->node, &sid->evsel->per_stream_periods);
+ hlist_add_head(&res->hnode, &sid->periods[hash]);
+
+ return &res->period;
}
void perf_counts_values__scale(struct perf_counts_values *count,
diff --git a/tools/lib/perf/include/internal/evsel.h b/tools/lib/perf/include/internal/evsel.h
index 5cd220a61962..ea78defa77d0 100644
--- a/tools/lib/perf/include/internal/evsel.h
+++ b/tools/lib/perf/include/internal/evsel.h
@@ -11,6 +11,32 @@
struct perf_thread_map;
struct xyarray;
+/**
+ * The per-thread accumulated period storage node.
+ */
+struct perf_sample_id_period {
+ struct list_head node;
+ struct hlist_node hnode;
+ /* Holds total ID period value for PERF_SAMPLE_READ processing. */
+ u64 period;
+ /* The TID that the values belongs to */
+ u32 tid;
+};
+
+/**
+ * perf_evsel_for_each_per_thread_period_safe - safely iterate thru all the
+ * per_stream_periods
+ * @evlist:perf_evsel instance to iterate
+ * @item: struct perf_sample_id_period iterator
+ * @tmp: struct perf_sample_id_period temp iterator
+ */
+#define perf_evsel_for_each_per_thread_period_safe(evsel, tmp, item) \
+ list_for_each_entry_safe(item, tmp, &(evsel)->per_stream_periods, node)
+
+
+#define PERF_SAMPLE_ID__HLIST_BITS 4
+#define PERF_SAMPLE_ID__HLIST_SIZE (1 << PERF_SAMPLE_ID__HLIST_BITS)
+
/*
* Per fd, to map back from PERF_SAMPLE_ID to evsel, only used when there are
* more than one entry in the evlist.
@@ -34,8 +60,32 @@ struct perf_sample_id {
pid_t machine_pid;
struct perf_cpu vcpu;
- /* Holds total ID period value for PERF_SAMPLE_READ processing. */
- u64 period;
+ /*
+ * Per-thread, and global event counts are mutually exclusive:
+ * Whilst it is possible to combine events into a group with differing
+ * values of PERF_SAMPLE_READ, it is not valid to have inconsistent
+ * values for `inherit`. Therefore it is not possible to have a
+ * situation where a per-thread event is sampled as a global event;
+ * all !inherit groups are global, and all groups where the sampling
+ * event is inherit + PERF_SAMPLE_READ will be per-thread. Any event
+ * that is part of such a group that is inherit but not PERF_SAMPLE_READ
+ * will be read as per-thread. If such an event can also trigger a
+ * sample (such as with sample_period > 0) then it will not cause
+ * `read_format` to be included in its PERF_RECORD_SAMPLE, and
+ * therefore will not expose the per-thread group members as global.
+ */
+ union {
+ /*
+ * Holds total ID period value for PERF_SAMPLE_READ processing
+ * (when period is not per-thread).
+ */
+ u64 period;
+ /*
+ * Holds total ID period value for PERF_SAMPLE_READ processing
+ * (when period is per-thread).
+ */
+ struct hlist_head periods[PERF_SAMPLE_ID__HLIST_SIZE];
+ };
};
struct perf_evsel {
@@ -58,6 +108,10 @@ struct perf_evsel {
u32 ids;
struct perf_evsel *leader;
+ /* For events where the read_format value is per-thread rather than
+ * global, stores the per-thread cumulative period */
+ struct list_head per_stream_periods;
+
/* parse modifier helper */
int nr_members;
/*
@@ -88,4 +142,9 @@ int perf_evsel__apply_filter(struct perf_evsel *evsel, const char *filter);
int perf_evsel__alloc_id(struct perf_evsel *evsel, int ncpus, int nthreads);
void perf_evsel__free_id(struct perf_evsel *evsel);
+bool perf_evsel__attr_has_per_thread_sample_period(struct perf_evsel *evsel);
+
+u64 *perf_sample_id__get_period_storage(struct perf_sample_id *sid, u32 tid,
+ bool per_thread);
+
#endif /* __LIBPERF_INTERNAL_EVSEL_H */
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index a10343b9dcd4..3515024986d5 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1474,18 +1474,24 @@ static int deliver_sample_value(struct evlist *evlist,
union perf_event *event,
struct perf_sample *sample,
struct sample_read_value *v,
- struct machine *machine)
+ struct machine *machine,
+ bool per_thread)
{
struct perf_sample_id *sid = evlist__id2sid(evlist, v->id);
struct evsel *evsel;
+ u64 *storage = NULL;
if (sid) {
+ storage = perf_sample_id__get_period_storage(sid, sample->tid, per_thread);
+ }
+
+ if (storage) {
sample->id = v->id;
- sample->period = v->value - sid->period;
- sid->period = v->value;
+ sample->period = v->value - *storage;
+ *storage = v->value;
}
- if (!sid || sid->evsel == NULL) {
+ if (!storage || sid->evsel == NULL) {
++evlist->stats.nr_unknown_id;
return 0;
}
@@ -1506,14 +1512,15 @@ static int deliver_sample_group(struct evlist *evlist,
union perf_event *event,
struct perf_sample *sample,
struct machine *machine,
- u64 read_format)
+ u64 read_format,
+ bool per_thread)
{
int ret = -EINVAL;
struct sample_read_value *v = sample->read.group.values;
sample_read_group__for_each(v, sample->read.group.nr, read_format) {
ret = deliver_sample_value(evlist, tool, event, sample, v,
- machine);
+ machine, per_thread);
if (ret)
break;
}
@@ -1528,6 +1535,7 @@ static int evlist__deliver_sample(struct evlist *evlist, struct perf_tool *tool,
/* We know evsel != NULL. */
u64 sample_type = evsel->core.attr.sample_type;
u64 read_format = evsel->core.attr.read_format;
+ bool per_thread = perf_evsel__attr_has_per_thread_sample_period(&evsel->core);
/* Standard sample delivery. */
if (!(sample_type & PERF_SAMPLE_READ))
@@ -1536,10 +1544,11 @@ static int evlist__deliver_sample(struct evlist *evlist, struct perf_tool *tool,
/* For PERF_SAMPLE_READ we have either single or group mode. */
if (read_format & PERF_FORMAT_GROUP)
return deliver_sample_group(evlist, tool, event, sample,
- machine, read_format);
+ machine, read_format, per_thread);
else
return deliver_sample_value(evlist, tool, event, sample,
- &sample->read.one, machine);
+ &sample->read.one, machine,
+ per_thread);
}
static int machines__deliver_event(struct machines *machines,
--
2.45.2
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