[heap] Add flags for predictable GC schedule

Provide flag to set a deterministic GC schedule. The GC still uses
multiple tasks but on a fixed growing strategy.

Change-Id: I937cf77ae0b0d1e513d4976a23c7f23a151d77c5
Reviewed-on: https://chromium-review.googlesource.com/c/1270838
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56498}

src/flag-definitions.h

@@ -825,6 +825,8 @@ DEFINE_BOOL(young_generation_large_objects, false,
             "allocates large objects by default in the young generation large "
             "object space")
 
+DEFINE_BOOL(idle_time_scavenge, true, "Perform scavenges in idle time.")
+
 // assembler-ia32.cc / assembler-arm.cc / assembler-x64.cc
 DEFINE_BOOL(debug_code, DEBUG_BOOL,
             "generate extra code (assertions) for debugging")
@@ -1393,6 +1395,15 @@ DEFINE_NEG_IMPLICATION(predictable, memory_reducer)
 DEFINE_VALUE_IMPLICATION(single_threaded, wasm_num_compilation_tasks, 0)
 DEFINE_NEG_IMPLICATION(single_threaded, wasm_async_compilation)
 
+DEFINE_BOOL(predictable_gc_schedule, false,
+            "Predictable garbage collection schedule. Fixes heap growing, "
+            "idle, and memory reducing behavior.")
+DEFINE_VALUE_IMPLICATION(predictable_gc_schedule, min_semi_space_size, 4)
+DEFINE_VALUE_IMPLICATION(predictable_gc_schedule, max_semi_space_size, 4)
+DEFINE_VALUE_IMPLICATION(predictable_gc_schedule, heap_growing_percent, 30)
+DEFINE_NEG_IMPLICATION(predictable_gc_schedule, idle_time_scavenge)
+DEFINE_NEG_IMPLICATION(predictable_gc_schedule, memory_reducer)
+
 //
 // Threading related flags.
 //

src/heap/heap.cc

@@ -982,6 +982,8 @@ void Heap::HandleGCRequest() {
 
 
 void Heap::ScheduleIdleScavengeIfNeeded(int bytes_allocated) {
+  DCHECK(FLAG_idle_time_scavenge);
+  DCHECK_NOT_NULL(scavenge_job_);
   scavenge_job_->ScheduleIdleTaskIfNeeded(this, bytes_allocated);
 }
 
@@ -4387,7 +4389,6 @@ void Heap::SetUp() {
     live_object_stats_ = new ObjectStats(this);
     dead_object_stats_ = new ObjectStats(this);
   }
-  scavenge_job_ = new ScavengeJob();
   local_embedder_heap_tracer_ = new LocalEmbedderHeapTracer(isolate());
 
   LOG(isolate_, IntPtrTEvent("heap-capacity", Capacity()));
@@ -4402,9 +4403,12 @@ void Heap::SetUp() {
   }
 #endif  // ENABLE_MINOR_MC
 
+  if (FLAG_idle_time_scavenge) {
+    scavenge_job_ = new ScavengeJob();
     idle_scavenge_observer_ = new IdleScavengeObserver(
         *this, ScavengeJob::kBytesAllocatedBeforeNextIdleTask);
     new_space()->AddAllocationObserver(idle_scavenge_observer_);
+  }
 
   SetGetExternallyAllocatedMemoryInBytesCallback(
       DefaultGetExternallyAllocatedMemoryInBytesCallback);
@@ -4568,9 +4572,13 @@ void Heap::TearDown() {
     }
   }
 
+  if (FLAG_idle_time_scavenge) {
     new_space()->RemoveAllocationObserver(idle_scavenge_observer_);
     delete idle_scavenge_observer_;
     idle_scavenge_observer_ = nullptr;
+    delete scavenge_job_;
+    scavenge_job_ = nullptr;
+  }
 
   if (FLAG_stress_marking > 0) {
     RemoveAllocationObserversFromAllSpaces(stress_marking_observer_,
@@ -4641,9 +4649,6 @@ void Heap::TearDown() {
   delete local_embedder_heap_tracer_;
   local_embedder_heap_tracer_ = nullptr;
 
-  delete scavenge_job_;
-  scavenge_job_ = nullptr;
-
   external_string_table_.TearDown();
 
   // Tear down all ArrayBuffers before tearing down the heap since  their