Just print interesting idle notification events in --trace-idle-notification.

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 4467 matching lines @@
   if (actual_time_in_ms <= idle_time_in_ms) {
     if (action.type != DONE && action.type != DO_NOTHING) {
       isolate()->counters()->gc_idle_time_limit_undershot()->AddSample(
           idle_time_in_ms - actual_time_in_ms);
     }
   } else {
     isolate()->counters()->gc_idle_time_limit_overshot()->AddSample(
         actual_time_in_ms - idle_time_in_ms);
   }
 
-  if (FLAG_trace_idle_notification) {
+  if ((FLAG_trace_idle_notification && action.type > DO_NOTHING) ||
+      FLAG_trace_idle_notification_verbose) {
     PrintF("Idle notification: requested idle time %d ms, actual time %d ms [",
            idle_time_in_ms, actual_time_in_ms);
     action.Print();
     PrintF("]");
     if (FLAG_trace_idle_notification_verbose) {
       PrintF("[");
       heap_state.Print();
       PrintF("]");
     }
     PrintF("\n");
@@ skipping 1817 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