Only add samples to the idle time undershoot histogram if we actually did gc

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 4334 matching lines @@
       break;
     case DO_FINALIZE_SWEEPING:
       mark_compact_collector()->EnsureSweepingCompleted();
       break;
     case DO_NOTHING:
       break;
   }
 
   int actual_time_ms = static_cast<int>(timer.Elapsed().InMilliseconds());
   if (actual_time_ms <= idle_time_in_ms) {
-    isolate()->counters()->gc_idle_time_limit_undershot()->AddSample(
-        idle_time_in_ms - actual_time_ms);
+    if (action.type != DONE && action.type != DO_NOTHING) {
+      isolate()->counters()->gc_idle_time_limit_undershot()->AddSample(
+          idle_time_in_ms - actual_time_ms);
+    }
   } else {
     isolate()->counters()->gc_idle_time_limit_overshot()->AddSample(
         actual_time_ms - idle_time_in_ms);
   }
 
   if (FLAG_trace_idle_notification) {
     PrintF("Idle notification: requested idle time %d ms, actual time %d ms [",
            idle_time_in_ms, actual_time_ms);
     action.Print();
     PrintF("]\n");
@@ skipping 1774 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 }
 }  // namespace v8::internal