perf expr: Migrate expr ids table to a hashmap

Use a hashmap between a char* string and a double* value. While bpf's
hashmap entries are size_t in size, we can't guarantee sizeof(size_t) >=
sizeof(double). Avoid a memory allocation when gathering ids by making
0.0 a special value encoded as NULL.

Original map suggestion by Andi Kleen:

  https://lore.kernel.org/lkml/20200224210308.GQ160988@tassilo.jf.intel.com/

and seconded by Jiri Olsa:

  https://lore.kernel.org/lkml/20200423112915.GH1136647@krava/

Committer notes:

There are fixes that need to land upstream before we can use libbpf's
headers, for now use our copy unconditionally, since the data structures
at this point are exactly the same, no problem.

When the fixes for libbpf's hashmap land upstream, we can fix this up.

Testing it:

Building with LIBBPF=1, i.e. the default:

  $ perf -vv | grep -i bpf
                     bpf: [ on  ]  # HAVE_LIBBPF_SUPPORT
  $ nm ~/bin/perf | grep -i libbpf_ | wc -l
  39
  $ nm ~/bin/perf | grep -i hashmap_ | wc -l
  17
  $

Explicitely building without LIBBPF:

  $ perf -vv | grep -i bpf
                     bpf: [ OFF ]  # HAVE_LIBBPF_SUPPORT
  $
  $ nm ~/bin/perf | grep -i libbpf_ | wc -l
  0
  $ nm ~/bin/perf | grep -i hashmap_ | wc -l
  9
  $

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kim Phillips <kim.phillips@amd.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org
Cc: kp singh <kpsingh@chromium.org>
Cc: netdev@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200515221732.44078-8-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 32 insertions, 17 deletions

diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
index 9bd7a8d2a858..c44dc814b377 100644
--- a/tools/perf/util/stat-shadow.c
+++ b/tools/perf/util/stat-shadow.c
@@ -323,35 +323,46 @@ void perf_stat__collect_metric_expr(struct evlist *evsel_list)
 {
 	struct evsel *counter, *leader, **metric_events, *oc;
 	bool found;
-	const char **metric_names;
+	struct expr_parse_ctx ctx;
+	struct hashmap_entry *cur;
+	size_t bkt;
 	int i;
-	int num_metric_names;
 
+	expr__ctx_init(&ctx);
 	evlist__for_each_entry(evsel_list, counter) {
 		bool invalid = false;
 
 		leader = counter->leader;
 		if (!counter->metric_expr)
 			continue;
+
+		expr__ctx_clear(&ctx);
 		metric_events = counter->metric_events;
 		if (!metric_events) {
-			if (expr__find_other(counter->metric_expr, counter->name,
-						&metric_names, &num_metric_names, 1) < 0)
+			if (expr__find_other(counter->metric_expr,
+					     counter->name,
+					     &ctx, 1) < 0)
 				continue;
 
 			metric_events = calloc(sizeof(struct evsel *),
-					       num_metric_names + 1);
-			if (!metric_events)
+					       hashmap__size(&ctx.ids) + 1);
+			if (!metric_events) {
+				expr__ctx_clear(&ctx);
 				return;
+			}
 			counter->metric_events = metric_events;
 		}
 
-		for (i = 0; i < num_metric_names; i++) {
+		i = 0;
+		hashmap__for_each_entry((&ctx.ids), cur, bkt) {
+			const char *metric_name = (const char *)cur->key;
+
 			found = false;
 			if (leader) {
 				/* Search in group */
 				for_each_group_member (oc, leader) {
-					if (!strcasecmp(oc->name, metric_names[i]) &&
+					if (!strcasecmp(oc->name,
+							metric_name) &&
 						!oc->collect_stat) {
 						found = true;
 						break;
@@ -360,7 +371,8 @@ void perf_stat__collect_metric_expr(struct evlist *evsel_list)
 			}
 			if (!found) {
 				/* Search ignoring groups */
-				oc = perf_stat__find_event(evsel_list, metric_names[i]);
+				oc = perf_stat__find_event(evsel_list,
+							   metric_name);
 			}
 			if (!oc) {
 				/* Deduping one is good enough to handle duplicated PMUs. */
@@ -373,27 +385,28 @@ void perf_stat__collect_metric_expr(struct evlist *evsel_list)
 				 * of events. So we ask the user instead to add the missing
 				 * events.
 				 */
-				if (!printed || strcasecmp(printed, metric_names[i])) {
+				if (!printed ||
+				    strcasecmp(printed, metric_name)) {
 					fprintf(stderr,
 						"Add %s event to groups to get metric expression for %s\n",
-						metric_names[i],
+						metric_name,
 						counter->name);
-					printed = strdup(metric_names[i]);
+					printed = strdup(metric_name);
 				}
 				invalid = true;
 				continue;
 			}
-			metric_events[i] = oc;
+			metric_events[i++] = oc;
 			oc->collect_stat = true;
 		}
 		metric_events[i] = NULL;
-		free(metric_names);
 		if (invalid) {
 			free(metric_events);
 			counter->metric_events = NULL;
 			counter->metric_expr = NULL;
 		}
 	}
+	expr__ctx_clear(&ctx);
 }
 
 static double runtime_stat_avg(struct runtime_stat *st,
@@ -738,7 +751,10 @@ static void generic_metric(struct perf_stat_config *config,
 
 	expr__ctx_init(&pctx);
 	/* Must be first id entry */
-	expr__add_id(&pctx, name, avg);
+	n = strdup(name);
+	if (!n)
+		return;
+	expr__add_id(&pctx, n, avg);
 	for (i = 0; metric_events[i]; i++) {
 		struct saved_value *v;
 		struct stats *stats;
@@ -814,8 +830,7 @@ static void generic_metric(struct perf_stat_config *config,
 			     (metric_name ? metric_name : name) : "", 0);
 	}
 
-	for (i = 1; i < pctx.num_ids; i++)
-		zfree(&pctx.ids[i].name);
+	expr__ctx_clear(&pctx);
 }
 
 void perf_stat__print_shadow_stats(struct perf_stat_config *config,