[heap] Use larger marking steps during external allocation pressure

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/heap/heap.h"
 
 #include <unordered_map>
 #include <unordered_set>
 
 #include "src/accessors.h"
@@ skipping 935 matching lines @@
               kGCCallbackFlagSynchronousPhantomCallbackProcessing |
               kGCCallbackFlagCollectAllExternalMemory));
     } else {
       CollectAllGarbage(i::Heap::kNoGCFlags,
                         GarbageCollectionReason::kExternalMemoryPressure,
                         kGCCallbackFlagSynchronousPhantomCallbackProcessing);
     }
   } else {
     // Incremental marking is turned on an has already been started.
     const double pressure =
-        static_cast<double>(external_memory_ -
-                            external_memory_at_last_mark_compact_ -
-                            kExternalAllocationSoftLimit) /
-        external_memory_hard_limit();
-    DCHECK_GE(1, pressure);
-    const double kMaxStepSizeOnExternalLimit = 25;
+        static_cast<double>(external_memory_) / external_memory_limit_;
+    DCHECK_LE(1.0, pressure);
+    const double kMinStepSize = 5;
+    const double kMaxStepSize = 10;
     const double deadline = MonotonicallyIncreasingTimeInMs() +
-                            pressure * kMaxStepSizeOnExternalLimit;
+                            Min(pressure * kMinStepSize, kMaxStepSize);
     incremental_marking()->AdvanceIncrementalMarking(
         deadline, IncrementalMarking::GC_VIA_STACK_GUARD,
         IncrementalMarking::FORCE_COMPLETION, StepOrigin::kV8);
   }
 }
 
 void Heap::EnsureFillerObjectAtTop() {
   // There may be an allocation memento behind objects in new space. Upon
   // evacuation of a non-full new space (or if we are on the last page) there
   // may be uninitialized memory behind top. We fill the remainder of the page
@@ skipping 5639 matching lines @@
     case LO_SPACE:
       return "LO_SPACE";
     default:
       UNREACHABLE();
   }
   return NULL;
 }
 
 }  // namespace internal
 }  // namespace v8