[heap] Evacuation for young generation

src/heap/spaces.cc

Index: src/heap/spaces.cc
diff --git a/src/heap/spaces.cc b/src/heap/spaces.cc
index 070b72c7bd9e8a035ade3f8c86d3eec3b2482703..d264cd07f8f1fc732dee6dfca26148137e8589d3 100644
--- a/src/heap/spaces.cc
+++ b/src/heap/spaces.cc
@@ -1295,6 +1295,15 @@ void PagedSpace::RefillFreeList() {
         p->Unlink();
         p->set_owner(this);
         p->InsertAfter(anchor_.prev_page());
+      } else {
+        CHECK_EQ(this, p->owner());
+        // Regular refill on main thread. Pages are already linked into the
+        // space but might require relinking.
+        if (p->available_in_free_list() < kPageReuseThreshold) {
+          // Relink categories with only little memory left previous to anchor.
+          p->Unlink();
+          p->InsertAfter(anchor()->prev_page());
+        }
       }
       added += RelinkFreeListCategories(p);
       added += p->wasted_memory();
@@ -1331,7 +1340,12 @@ void PagedSpace::MergeCompactionSpace(CompactionSpace* other) {
 
     p->Unlink();
     p->set_owner(this);
-    p->InsertAfter(anchor_.prev_page());
+    if (p->available_in_free_list() < kPageReuseThreshold) {
+      // Relink categories with only little memory left previous to anchor.
+      p->InsertAfter(anchor()->prev_page());
+    } else {
+      p->InsertAfter(anchor());
+    }
     RelinkFreeListCategories(p);
     DCHECK_EQ(p->AvailableInFreeList(), p->available_in_free_list());
   }
@@ -1356,6 +1370,31 @@ bool PagedSpace::ContainsSlow(Address addr) {
   return false;
 }
 
+Page* PagedSpace::RemovePageSafe() {
+  base::LockGuard<base::Mutex> guard(mutex());
+  Page* page = anchor()->next_page();
+
+  while (!page->CanUseForAllocation()) page = page->next_page();
+  if (page == anchor() || page->available_in_free_list() < kPageReuseThreshold)
+    return nullptr;
+
+  AccountUncommitted(page->size());
+  accounting_stats_.DeallocateBytes(page->LiveBytesFromFreeList());
+  accounting_stats_.DecreaseCapacity(page->area_size());
+  page->Unlink();
+  UnlinkFreeListCategories(page);
+  return page;
+}
+
+void PagedSpace::AddPage(Page* page) {
+  AccountCommitted(page->size());
+  accounting_stats_.IncreaseCapacity(page->area_size());
+  accounting_stats_.AllocateBytes(page->LiveBytesFromFreeList());
+  page->set_owner(this);
+  RelinkFreeListCategories(page);
+  page->InsertAfter(anchor()->prev_page());
+}
+
 void PagedSpace::ShrinkImmortalImmovablePages() {
   DCHECK(!heap()->deserialization_complete());
   MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
@@ -1371,6 +1410,8 @@ void PagedSpace::ShrinkImmortalImmovablePages() {
 }
 
 bool PagedSpace::Expand() {
+  base::LockGuard<base::Mutex> guard(mutex());
+
   const int size = AreaSize();
 
   if (!heap()->CanExpandOldGeneration(size)) return false;
@@ -2918,6 +2959,17 @@ HeapObject* PagedSpace::SlowAllocateRaw(int size_in_bytes) {
       object = free_list_.Allocate(static_cast<size_t>(size_in_bytes));
       if (object != nullptr) return object;
     }
+  } else if (is_local()) {
+    // Sweeping not in progress and we are on a {CompactionSpace}. This can
+    // only happen when we are evacuating for the young generation.
+    PagedSpace* main_space = heap()->paged_space(identity());
+    Page* page = main_space->RemovePageSafe();
+    if (page != nullptr) {
+      AddPage(page);
+      HeapObject* object =
+          free_list_.Allocate(static_cast<size_t>(size_in_bytes));
+      if (object != nullptr) return object;
+    }
   }
 
   if (heap()->ShouldExpandOldGenerationOnSlowAllocation() && Expand()) {