perf pmu: Parse sysfs events directly from a file

Rather than read a sysfs events file into a 256 byte char buffer, pass
the FILE* directly to the lex/yacc parser.

This avoids there being a maximum events file size.

While changing the API, constify some arguments to remove unnecessary
casts.

Allocating the read buffer decreases the performance of pmu-scan by
around 3%.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Gaosheng Cui <cuigaosheng1@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230824041330.266337-10-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 781747bedc3e..c71e135d7335 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1715,6 +1715,7 @@ int parse_events_name(struct list_head *list, const char *name)
 }
 
 static int parse_events__scanner(const char *str,
+				 FILE *input,
 				 struct parse_events_state *parse_state)
 {
 	YY_BUFFER_STATE buffer;
@@ -1725,7 +1726,10 @@ static int parse_events__scanner(const char *str,
 	if (ret)
 		return ret;
 
-	buffer = parse_events__scan_string(str, scanner);
+	if (str)
+		buffer = parse_events__scan_string(str, scanner);
+	else
+	        parse_events_set_in(input, scanner);
 
 #ifdef PARSER_DEBUG
 	parse_events_debug = 1;
@@ -1733,8 +1737,10 @@ static int parse_events__scanner(const char *str,
 #endif
 	ret = parse_events_parse(parse_state, scanner);
 
-	parse_events__flush_buffer(buffer, scanner);
-	parse_events__delete_buffer(buffer, scanner);
+	if (str) {
+		parse_events__flush_buffer(buffer, scanner);
+		parse_events__delete_buffer(buffer, scanner);
+	}
 	parse_events_lex_destroy(scanner);
 	return ret;
 }
@@ -1742,7 +1748,7 @@ static int parse_events__scanner(const char *str,
 /*
  * parse event config string, return a list of event terms.
  */
-int parse_events_terms(struct list_head *terms, const char *str)
+int parse_events_terms(struct list_head *terms, const char *str, FILE *input)
 {
 	struct parse_events_state parse_state = {
 		.terms  = NULL,
@@ -1750,7 +1756,7 @@ int parse_events_terms(struct list_head *terms, const char *str)
 	};
 	int ret;
 
-	ret = parse_events__scanner(str, &parse_state);
+	ret = parse_events__scanner(str, input, &parse_state);
 
 	if (!ret) {
 		list_splice(parse_state.terms, terms);
@@ -2001,7 +2007,7 @@ int __parse_events(struct evlist *evlist, const char *str, const char *pmu_filte
 	};
 	int ret, ret2;
 
-	ret = parse_events__scanner(str, &parse_state);
+	ret = parse_events__scanner(str, /*input=*/ NULL, &parse_state);
 
 	if (!ret && list_empty(&parse_state.list)) {
 		WARN_ONCE(true, "WARNING: event parser found nothing\n");