[heap] Add a flag for performing incremental marking on allocation

The flag is true by default and passing
--noincremental-marking-on-allocation disables starting of incremental
marking on allocation and incremental marking steps on allocation.

Change-Id: I4537e0eeaaf93fb713fcacd3860e29b98df441fc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2154194Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67228}

src/flags/flag-definitions.h

@@ -892,6 +892,8 @@ DEFINE_BOOL(incremental_marking, true, "use incremental marking")
 DEFINE_BOOL(incremental_marking_wrappers, true,
             "use incremental marking for marking wrappers")
 DEFINE_BOOL(incremental_marking_task, true, "use tasks for incremental marking")
+DEFINE_BOOL(incremental_marking_on_allocation, false,
+            "incremental marking on allocation")
 DEFINE_INT(incremental_marking_soft_trigger, 0,
            "threshold for starting incremental marking via a task in percent "
            "of available space: limit - size")

src/heap/heap.cc

@@ -1670,6 +1670,11 @@ int Heap::NotifyContextDisposed(bool dependant_context) {
 void Heap::StartIncrementalMarking(int gc_flags,
                                    GarbageCollectionReason gc_reason,
                                    GCCallbackFlags gc_callback_flags) {
+  if (V8_UNLIKELY(!FLAG_incremental_marking_on_allocation) &&
+      (gc_reason == GarbageCollectionReason::kAllocationLimit ||
+       gc_reason == GarbageCollectionReason::kGlobalAllocationLimit)) {
+    return;
+  }
   DCHECK(incremental_marking()->IsStopped());
   set_current_gc_flags(gc_flags);
   current_gc_callback_flags_ = gc_callback_flags;

src/heap/incremental-marking.cc

@@ -1036,7 +1036,8 @@ void IncrementalMarking::AdvanceOnAllocation() {
   // Code using an AlwaysAllocateScope assumes that the GC state does not
   // change; that implies that no marking steps must be performed.
   if (heap_->gc_state() != Heap::NOT_IN_GC || !FLAG_incremental_marking ||
-      (state_ != SWEEPING && state_ != MARKING) || heap_->always_allocate()) {
+      (state_ != SWEEPING && state_ != MARKING) || heap_->always_allocate() ||
+      V8_UNLIKELY(!FLAG_incremental_marking_on_allocation)) {
     return;
   }
   HistogramTimerScope incremental_marking_scope(