perf tools: Cache counter names for raw samples on s390

Searching all event names is slower now that legacy names are
included. Add a cache to avoid long iterative searches. Note, the
cache isn't cleaned up and is as such a memory leak, however, globally
reachable leaks like this aren't treated as leaks by leak sanitizer.

Reported-by: Thomas Richter <tmricht@linux.ibm.com>
Closes: https://lore.kernel.org/linux-perf-users/09943f4f-516c-4b93-877c-e4a64ed61d38@linux.ibm.com/
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

diff --git a/tools/perf/util/s390-sample-raw.c b/tools/perf/util/s390-sample-raw.c
index 335217bb532b427b010cff7573435bb5b7e7fb9e..c6ae0ae8d86a3920b3dbafd21ef8b880145f23ba 100644 (file)
--- a/tools/perf/util/s390-sample-raw.c
+++ b/tools/perf/util/s390-sample-raw.c
@@ -19,12 +19,14 @@
 
 #include <sys/stat.h>
 #include <linux/compiler.h>
+#include <linux/err.h>
 #include <asm/byteorder.h>
 
 #include "debug.h"
 #include "session.h"
 #include "evlist.h"
 #include "color.h"
+#include "hashmap.h"
 #include "sample-raw.h"
 #include "s390-cpumcf-kernel.h"
 #include "util/pmu.h"
@@ -132,8 +134,8 @@ static int get_counterset_start(int setnr)
 }
 
 struct get_counter_name_data {
-       int wanted;
-       char *result;
+       long wanted;
+       const char *result;
 };
 
 static int get_counter_name_callback(void *vdata, struct pmu_event_info *info)
@@ -151,12 +153,22 @@ static int get_counter_name_callback(void *vdata, struct pmu_event_info *info)
 
        rc = sscanf(event_str, "event=%x", &event_nr);
        if (rc == 1 && event_nr == data->wanted) {
-               data->result = strdup(info->name);
+               data->result = info->name;
                return 1; /* Terminate the search. */
        }
        return 0;
 }
 
+static size_t get_counter_name_hash_fn(long key, void *ctx __maybe_unused)
+{
+       return key;
+}
+
+static bool get_counter_name_hashmap_equal_fn(long key1, long key2, void *ctx __maybe_unused)
+{
+       return key1 == key2;
+}
+
 /* Scan the PMU and extract the logical name of a counter from the event. Input
  * is the counter set and counter number with in the set. Construct the event
  * number and use this as key. If they match return the name of this counter.
@@ -164,17 +176,50 @@ static int get_counter_name_callback(void *vdata, struct pmu_event_info *info)
  */
 static char *get_counter_name(int set, int nr, struct perf_pmu *pmu)
 {
+       static struct hashmap *cache;
+       static struct perf_pmu *cache_pmu;
+       long cache_key = get_counterset_start(set) + nr;
        struct get_counter_name_data data = {
-               .wanted = get_counterset_start(set) + nr,
+               .wanted = cache_key,
                .result = NULL,
        };
+       char *result = NULL;
 
        if (!pmu)
                return NULL;
 
+       if (cache_pmu == pmu && hashmap__find(cache, cache_key, &result))
+               return strdup(result);
+
        perf_pmu__for_each_event(pmu, /*skip_duplicate_pmus=*/ true,
                                 &data, get_counter_name_callback);
-       return data.result;
+
+       result = strdup(data.result ?: "<unknown>");
+
+       if (cache_pmu == NULL) {
+               struct hashmap *tmp = hashmap__new(get_counter_name_hash_fn,
+                                                  get_counter_name_hashmap_equal_fn,
+                                                  /*ctx=*/NULL);
+
+               if (!IS_ERR(tmp)) {
+                       cache = tmp;
+                       cache_pmu = pmu;
+               }
+       }
+
+       if (cache_pmu == pmu && result) {
+               char *old_value = NULL, *new_value = strdup(result);
+
+               if (new_value) {
+                       hashmap__set(cache, cache_key, new_value, /*old_key=*/NULL, &old_value);
+                       /*
+                        * Free in case of a race, but resizing would be broken
+                        * in that case.
+                        */
+                       free(old_value);
+               }
+       }
+       return result;
 }
 
 static void s390_cpumcfdg_dump(struct perf_pmu *pmu, struct perf_sample *sample)