MXS-2078 Take new statistics into use

maxutils/maxbase/include/maxbase/stopwatch.hh

@@ -37,12 +37,14 @@ struct Duration : public Clock::duration
 {
     using Clock::duration::duration;
     Duration() = default;
-    Duration(Clock::duration d) : Clock::duration(d)
+    Duration(Clock::duration d)
+        : Clock::duration(d)
     {
     }
 
     /** From seconds */
-    explicit Duration(double secs) : Duration{rep(secs * period::den / period::num)}
+    explicit Duration(double secs)
+        : Duration{rep(secs * period::den / period::num)}
     {
     }
 
@@ -125,7 +127,7 @@ public:
     /** Resume measuring time. Ok to call multiple times without an end_interval(). */
     void start_interval();
 
-    /** Pause measuring time. */
+    /** Pause measuring time. Ok to call without a start_interval. */
     void end_interval();
 
     /** Total duration of intervals (thus far). */

maxutils/maxbase/src/stopwatch.cc

@@ -47,7 +47,8 @@ Duration StopWatch::restart()
     return split;
 }
 
-IntervalTimer::IntervalTimer() : m_total(0)
+IntervalTimer::IntervalTimer()
+    : m_total(0)
 {
 }
 
@@ -58,6 +59,12 @@ void IntervalTimer::start_interval()
 
 void IntervalTimer::end_interval()
 {
+    if (m_last_start == maxbase::TimePoint())
+    {
+        // m_last_start is defaulted. Ignore, avoids extra logic at call sites.
+        return;
+    }
+
     m_total += Clock::now() - m_last_start;
     // reset to make it easier to spot usage bugs, like calling end_interval(); end_interval();
     m_last_start = TimePoint();