mon/scrub: add mon scrub latency

If mon store.db very big, scrub will be a very
time-consuming operation.

Fixes: https://tracker.ceph.com/issues/66873
Signed-off-by: Yite Gu <[email protected]>

Author: YiteGu

src/mon/Monitor.cc

@@ -5661,10 +5661,13 @@ void Monitor::handle_scrub(MonOpRequestRef op)
       if (scrub_result.size() == quorum.size()) {
         scrub_check_results();
         scrub_result.clear();
-        if (scrub_state->finished)
+        if (scrub_state->finished) {
+          const utime_t lat = ceph_clock_now() - scrub_state->start;
+          dout(10) << __func__ << " mon scrub latency: " << lat << dendl;
           scrub_finish();
-        else
+        } else {
           scrub();
+        }
       }
     }
     break;

src/mon/Monitor.h

@@ -341,8 +341,10 @@ class Monitor : public Dispatcher,
   struct ScrubState {
     std::pair<std::string,std::string> last_key; ///< last scrubbed key
     bool finished;
+    const utime_t start;
 
-    ScrubState() : finished(false) { }
+    ScrubState() : finished(false),
+                   start(ceph_clock_now()) { }
     virtual ~ScrubState() { }
   };
   std::shared_ptr<ScrubState> scrub_state; ///< keeps track of current scrub