parse-events: Cache last event found

Code commonly passes around the event id and uses that to find the
event. Even if the event was already found, it uses the id to find
it later.

By caching the last event found by the name or id, and checking that
on the next query before searching, saves some time.

Running trace-cmd report on 6,000,000 events went from:

 real	0m41.805s
 user	0m39.483s
 sys	0m2.311s

to:

 real	0m39.769s
 user	0m37.401s
 sys	0m2.356s

About a 4% speed-up.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 16 insertions, 1 deletions

diff --git a/parse-events.c b/parse-events.c
index 7e0336b..db60c7b 100644
--- a/parse-events.c
+++ b/parse-events.c
@@ -2609,13 +2609,19 @@ struct event_format *pevent_find_event(struct pevent *pevent, int id)
         struct event_format key;
         struct event_format *pkey = &key;
 
+        /* Check cache first */
+        if (pevent->last_event && pevent->last_event->id == id)
+                return pevent->last_event;
+
         key.id = id;
 
         eventptr = bsearch(&pkey, pevent->events, pevent->nr_events,
                            sizeof(*pevent->events), events_id_cmp);
 
-        if (eventptr)
+        if (eventptr) {
+                pevent->last_event = *eventptr;
                 return *eventptr;
+        }
 
         return NULL;
 }
@@ -2636,6 +2642,11 @@ pevent_find_event_by_name(struct pevent *pevent,
         struct event_format *event;
         int i;
 
+        if (pevent->last_event &&
+            strcmp(pevent->last_event->name, name) == 0 &&
+            (!sys || strcmp(pevent->last_event->system, sys) == 0))
+                return pevent->last_event;
+
         for (i = 0; i < pevent->nr_events; i++) {
                 event = pevent->events[i];
                 if (strcmp(event->name, name) == 0) {
@@ -2648,6 +2659,7 @@ pevent_find_event_by_name(struct pevent *pevent,
         if (i == pevent->nr_events)
                 event = NULL;
 
+        pevent->last_event = event;
         return event;
 }
 
diff --git a/parse-events.h b/parse-events.h
index 4aa83f7..73fc2ea 100644
--- a/parse-events.h
+++ b/parse-events.h
@@ -313,6 +313,9 @@ struct pevent {
         struct format_field *bprint_ip_field;
         struct format_field *bprint_fmt_field;
         struct format_field *bprint_buf_field;
+
+        /* cache */
+        struct event_format *last_event;
 };
 
 void die(char *fmt, ...);