[heap] Reland "Use RAIL mode for initial heap sizing"

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 "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/context-slot-cache.h"
 #include "src/base/bits.h"
@@ skipping 5286 matching lines @@
           "Dampen: old size: %" PRIuS " KB, old limit: %" PRIuS
           " KB, "
           "new limit: %" PRIuS " KB (%.1f)\n",
           old_gen_size / KB, old_generation_allocation_limit_ / KB, limit / KB,
           factor);
     }
     old_generation_allocation_limit_ = limit;
   }
 }
 
+bool Heap::ShouldOptimizeForLoadTime() {
+  return isolate()->rail_mode() == PERFORMANCE_LOAD &&
+         PromotedTotalSize() < initial_old_generation_size_ &&
+         MonotonicallyIncreasingTimeInMs() <
+             isolate()->LoadStartTimeMs() + kMaxLoadTimeMs;
+}
+
 // This predicate is called when an old generation space cannot allocated from
 // the free list and is about to add a new page. Returning false will cause a
 // major GC. It happens when the old generation allocation limit is reached and
 // - either we need to optimize for memory usage,
 // - or the incremental marking is not in progress and we cannot start it.
 bool Heap::ShouldExpandOldGenerationOnSlowAllocation() {
   if (always_allocate() || OldGenerationSpaceAvailable() > 0) return true;
   // We reached the old generation allocation limit.
 
   if (ShouldOptimizeForMemoryUsage()) return false;
 
+  if (ShouldOptimizeForLoadTime()) return true;
+
   if (incremental_marking()->NeedsFinalization()) {
     return !AllocationLimitOvershotByLargeMargin();
   }
 
   if (incremental_marking()->IsStopped() &&
       IncrementalMarkingLimitReached() == IncrementalMarkingLimit::kNoLimit) {
     // We cannot start incremental marking.
     return false;
   }
   return true;
@@ skipping 1162 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8