[heap,snapshot] Replace first page size from snapshots with page trimming

test/cctest/heap/test-spaces.cc

Index: test/cctest/heap/test-spaces.cc
diff --git a/test/cctest/heap/test-spaces.cc b/test/cctest/heap/test-spaces.cc
index 818716a53dda21da98a30616fa9529f1086ba2d8..f485e7ffef9372f5ad5f3a1909808339e71afdb3 100644
--- a/test/cctest/heap/test-spaces.cc
+++ b/test/cctest/heap/test-spaces.cc
@@ -36,6 +36,7 @@
 #include "src/v8.h"
 #include "test/cctest/cctest.h"
 #include "test/cctest/heap/heap-tester.h"
+#include "test/cctest/heap/heap-utils.h"
 
 namespace v8 {
 namespace internal {
@@ -482,8 +483,7 @@ TEST(LargeObjectSpace) {
   CHECK(lo->AllocateRaw(lo_size, NOT_EXECUTABLE).IsRetry());
 }
 
-
-TEST(SizeOfFirstPageIsLargeEnough) {
+TEST(SizeOfInitialHeap) {
   if (i::FLAG_always_opt) return;
   // Bootstrapping without a snapshot causes more allocations.
   CcTest::InitializeVM();
@@ -499,22 +499,31 @@ TEST(SizeOfFirstPageIsLargeEnough) {
     return;
   }
 
-  // If this test fails due to enabling experimental natives that are not part
-  // of the snapshot, we may need to adjust CalculateFirstPageSizes.
+  // The limit for each space for an empty isolate containing just the
+  // snapshot.
+  const size_t kMaxInitialSizePerSpace = 2 * MB;
 
-  // Freshly initialized VM gets by with one page per space.
+  // Freshly initialized VM gets by with the snapshot size (which is below
+  // kMaxInitialSizePerSpace per space).
+  Heap* heap = isolate->heap();
+  int page_count[LAST_PAGED_SPACE + 1] = {0, 0, 0, 0};
   for (int i = FIRST_PAGED_SPACE; i <= LAST_PAGED_SPACE; i++) {
     // Debug code can be very large, so skip CODE_SPACE if we are generating it.
     if (i == CODE_SPACE && i::FLAG_debug_code) continue;
-    CHECK_EQ(1, isolate->heap()->paged_space(i)->CountTotalPages());
+
+    page_count[i] = heap->paged_space(i)->CountTotalPages();
+    // Check that the initial heap is also below the limit.
+    CHECK_LT(static_cast<size_t>(heap->paged_space(i)->CommittedMemory()),
+             kMaxInitialSizePerSpace);
   }
 
-  // Executing the empty script gets by with one page per space.
+  // Executing the empty script gets by with the same number of pages, i.e.,
+  // requires no extra space.
   CompileRun("/*empty*/");
   for (int i = FIRST_PAGED_SPACE; i <= LAST_PAGED_SPACE; i++) {
     // Debug code can be very large, so skip CODE_SPACE if we are generating it.
     if (i == CODE_SPACE && i::FLAG_debug_code) continue;
-    CHECK_EQ(1, isolate->heap()->paged_space(i)->CountTotalPages());
+    CHECK_EQ(page_count[i], isolate->heap()->paged_space(i)->CountTotalPages());
   }
 
   // No large objects required to perform the above steps.
@@ -685,5 +694,104 @@ UNINITIALIZED_TEST(InlineAllocationObserverCadence) {
   isolate->Dispose();
 }
 
+TEST(ShrinkPageToHighWaterMarkFreeSpaceEnd) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  HandleScope scope(isolate);
+
+  heap::SealCurrentObjects(CcTest::heap());
+
+  // Prepare page that only contains a single object and a trailing FreeSpace
+  // filler.
+  Handle<FixedArray> array = isolate->factory()->NewFixedArray(128, TENURED);
+  Page* page = Page::FromAddress(array->address());
+
+  // Reset space so high water mark is consistent.
+  CcTest::heap()->old_space()->ResetFreeList();
+  CcTest::heap()->old_space()->EmptyAllocationInfo();
+
+  HeapObject* filler =
+      HeapObject::FromAddress(array->address() + array->Size());
+  CHECK(filler->IsFreeSpace());
+  size_t shrinked = page->ShrinkToHighWaterMark();
+  size_t should_have_shrinked =
+      RoundDown(static_cast<size_t>(Page::kAllocatableMemory - array->Size()),
+                base::OS::CommitPageSize());
+  CHECK_EQ(should_have_shrinked, shrinked);
+}
+
+TEST(ShrinkPageToHighWaterMarkNoFiller) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  HandleScope scope(isolate);
+  heap::SealCurrentObjects(CcTest::heap());
+
+  const int kFillerSize = 0;
+  std::vector<Handle<FixedArray>> arrays =
+      heap::FillOldSpacePageWithFixedArrays(CcTest::heap(), kFillerSize);
+  Handle<FixedArray> array = arrays.back();
+  Page* page = Page::FromAddress(array->address());
+  CHECK_EQ(page->area_end(), array->address() + array->Size() + kFillerSize);
+
+  // Reset space so high water mark and fillers are consistent.
+  CcTest::heap()->old_space()->ResetFreeList();
+  CcTest::heap()->old_space()->EmptyAllocationInfo();
+
+  const size_t shrinked = page->ShrinkToHighWaterMark();
+  CHECK_EQ(0, shrinked);
+}
+
+TEST(ShrinkPageToHighWaterMarkOneWordFiller) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  HandleScope scope(isolate);
+
+  heap::SealCurrentObjects(CcTest::heap());
+
+  const int kFillerSize = kPointerSize;
+  std::vector<Handle<FixedArray>> arrays =
+      heap::FillOldSpacePageWithFixedArrays(CcTest::heap(), kFillerSize);
+  Handle<FixedArray> array = arrays.back();
+  Page* page = Page::FromAddress(array->address());
+  CHECK_EQ(page->area_end(), array->address() + array->Size() + kFillerSize);
+
+  // Reset space so high water mark and fillers are consistent.
+  CcTest::heap()->old_space()->ResetFreeList();
+  CcTest::heap()->old_space()->EmptyAllocationInfo();
+
+  HeapObject* filler =
+      HeapObject::FromAddress(array->address() + array->Size());
+  CHECK_EQ(filler->map(), CcTest::heap()->one_pointer_filler_map());
+
+  const size_t shrinked = page->ShrinkToHighWaterMark();
+  CHECK_EQ(0, shrinked);
+}
+
+TEST(ShrinkPageToHighWaterMarkTwoWordFiller) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  HandleScope scope(isolate);
+
+  heap::SealCurrentObjects(CcTest::heap());
+
+  const int kFillerSize = 2 * kPointerSize;
+  std::vector<Handle<FixedArray>> arrays =
+      heap::FillOldSpacePageWithFixedArrays(CcTest::heap(), kFillerSize);
+  Handle<FixedArray> array = arrays.back();
+  Page* page = Page::FromAddress(array->address());
+  CHECK_EQ(page->area_end(), array->address() + array->Size() + kFillerSize);
+
+  // Reset space so high water mark and fillers are consistent.
+  CcTest::heap()->old_space()->ResetFreeList();
+  CcTest::heap()->old_space()->EmptyAllocationInfo();
+
+  HeapObject* filler =
+      HeapObject::FromAddress(array->address() + array->Size());
+  CHECK_EQ(filler->map(), CcTest::heap()->two_pointer_filler_map());
+
+  const size_t shrinked = page->ShrinkToHighWaterMark();
+  CHECK_EQ(0, shrinked);
+}
+
 }  // namespace internal
 }  // namespace v8