[heap] Cache OS commit page size in MemoryAllocator

We can cache this in a static field during V8 initialization such that
we don't need to cache this method's result for each use-case that
might benefit.

Bug: v8:12691
Change-Id: I4391a5e306646465ce96fb7e354be996d9fe8b44
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3506375
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79406}

src/execution/isolate.cc

@@ -521,6 +521,8 @@ void Isolate::InitializeOncePerProcess() {
   CHECK(isolate_key_created_.compare_exchange_strong(
       expected, true, std::memory_order_relaxed));
   per_isolate_thread_data_key_ = base::Thread::CreateThreadLocalKey();
+
+  Heap::InitializeOncePerProcess();
 }
 
 void Isolate::DisposeOncePerProcess() {

src/heap/heap.cc

@@ -5835,6 +5835,11 @@ void Heap::InitializeHashSeed() {
       0, reinterpret_cast<byte*>(&new_hash_seed), kInt64Size);
 }
 
+// static
+void Heap::InitializeOncePerProcess() {
+  MemoryAllocator::InitializeOncePerProcess();
+}
+
 void Heap::PrintMaxMarkingLimitReached() {
   PrintF("\n### Maximum marking limit reached = %.02lf\n",
          max_marking_limit_reached_);

src/heap/heap.h

@@ -808,6 +808,9 @@ class Heap {
   // (Re-)Initialize hash seed from flag or RNG.
   void InitializeHashSeed();
 
+  // Invoked once for the process from V8::Initialize.
+  static void InitializeOncePerProcess();
+
   // Bootstraps the object heap with the core set of objects required to run.
   // Returns whether it succeeded.
   bool CreateHeapObjects();

src/heap/memory-allocator.cc

@@ -24,6 +24,9 @@ namespace internal {
 // MemoryAllocator
 //
 
+size_t MemoryAllocator::commit_page_size_ = 0;
+size_t MemoryAllocator::commit_page_size_bits_ = 0;
+
 MemoryAllocator::MemoryAllocator(Isolate* isolate,
                                  v8::PageAllocator* code_page_allocator,
                                  size_t capacity)
@@ -619,18 +622,16 @@ void MemoryAllocator::ZapBlock(Address start, size_t size,
                size >> kTaggedSizeLog2);
 }
 
-intptr_t MemoryAllocator::GetCommitPageSize() {
+void MemoryAllocator::InitializeOncePerProcess() {
-  if (FLAG_v8_os_page_size != 0) {
+  commit_page_size_ =
-    DCHECK(base::bits::IsPowerOfTwo(FLAG_v8_os_page_size));
+      FLAG_v8_os_page_size > 0 ? FLAG_v8_os_page_size * KB : CommitPageSize();
-    return FLAG_v8_os_page_size * KB;
+  CHECK(base::bits::IsPowerOfTwo(commit_page_size_));
-  } else {
+  commit_page_size_bits_ = base::bits::WhichPowerOfTwo(commit_page_size_);
-    return CommitPageSize();
-  }
 }
 
 base::AddressRegion MemoryAllocator::ComputeDiscardMemoryArea(Address addr,
                                                               size_t size) {
-  size_t page_size = MemoryAllocator::GetCommitPageSize();
+  size_t page_size = GetCommitPageSize();
   if (size < page_size + FreeSpace::kSize) {
     return base::AddressRegion(0, 0);
   }

src/heap/memory-allocator.h

@@ -153,7 +153,18 @@ class MemoryAllocator {
     kConcurrentlyAndPool,
   };
 
-  V8_EXPORT_PRIVATE static intptr_t GetCommitPageSize();
+  // Initialize page sizes field in V8::Initialize.
+  static void InitializeOncePerProcess();
+
+  V8_INLINE static intptr_t GetCommitPageSize() {
+    DCHECK_LT(0, commit_page_size_);
+    return commit_page_size_;
+  }
+
+  V8_INLINE static intptr_t GetCommitPageSizeBits() {
+    DCHECK_LT(0, commit_page_size_bits_);
+    return commit_page_size_bits_;
+  }
 
   // Computes the memory area of discardable memory within a given memory area
   // [addr, addr+size) and returns the result as base::AddressRegion. If the
@@ -383,6 +394,9 @@ class MemoryAllocator {
   base::Mutex executable_memory_mutex_;
 #endif  // DEBUG
 
+  V8_EXPORT_PRIVATE static size_t commit_page_size_;
+  V8_EXPORT_PRIVATE static size_t commit_page_size_bits_;
+
   friend class heap::TestCodePageAllocatorScope;
   friend class heap::TestMemoryAllocatorScope;
 

test/cctest/heap/test-spaces.cc

@@ -857,14 +857,12 @@ TEST(ReadOnlySpaceMetrics_OnePage) {
   faked_space->ShrinkPages();
   faked_space->Seal(ReadOnlySpace::SealMode::kDoNotDetachFromHeap);
 
-  MemoryAllocator* allocator = heap->memory_allocator();
-
   // Allocated objects size.
   CHECK_EQ(faked_space->Size(), 16);
 
   size_t committed_memory = RoundUp(
       MemoryChunkLayout::ObjectStartOffsetInDataPage() + faked_space->Size(),
-      allocator->GetCommitPageSize());
+      MemoryAllocator::GetCommitPageSize());
 
   // Amount of OS allocated memory.
   CHECK_EQ(faked_space->CommittedMemory(), committed_memory);
@@ -891,10 +889,9 @@ TEST(ReadOnlySpaceMetrics_AlignedAllocations) {
   CHECK_EQ(faked_space->CommittedMemory(), 0);
   CHECK_EQ(faked_space->CommittedPhysicalMemory(), 0);
 
-  MemoryAllocator* allocator = heap->memory_allocator();
   // Allocate an object just under an OS page in size.
   int object_size =
-      static_cast<int>(allocator->GetCommitPageSize() - kApiTaggedSize);
+      static_cast<int>(MemoryAllocator::GetCommitPageSize() - kApiTaggedSize);
 
 // TODO(v8:8875): Pointer compression does not enable aligned memory allocation
 // yet.
@@ -926,7 +923,7 @@ TEST(ReadOnlySpaceMetrics_AlignedAllocations) {
 
   size_t committed_memory = RoundUp(
       MemoryChunkLayout::ObjectStartOffsetInDataPage() + faked_space->Size(),
-      allocator->GetCommitPageSize());
+      MemoryAllocator::GetCommitPageSize());
 
   CHECK_EQ(faked_space->CommittedMemory(), committed_memory);
   CHECK_EQ(faked_space->CommittedPhysicalMemory(), committed_memory);
@@ -952,8 +949,6 @@ TEST(ReadOnlySpaceMetrics_TwoPages) {
   CHECK_EQ(faked_space->CommittedMemory(), 0);
   CHECK_EQ(faked_space->CommittedPhysicalMemory(), 0);
 
-  MemoryAllocator* allocator = heap->memory_allocator();
-
   // Allocate an object that's too big to have more than one on a page.
 
   int object_size = RoundUp(
@@ -976,7 +971,7 @@ TEST(ReadOnlySpaceMetrics_TwoPages) {
   // Amount of OS allocated memory.
   size_t committed_memory_per_page =
       RoundUp(MemoryChunkLayout::ObjectStartOffsetInDataPage() + object_size,
-              allocator->GetCommitPageSize());
+              MemoryAllocator::GetCommitPageSize());
   CHECK_EQ(faked_space->CommittedMemory(), 2 * committed_memory_per_page);
   CHECK_EQ(faked_space->CommittedPhysicalMemory(),
            2 * committed_memory_per_page);
@@ -985,7 +980,7 @@ TEST(ReadOnlySpaceMetrics_TwoPages) {
   // page headers.
   size_t capacity_per_page =
       RoundUp(MemoryChunkLayout::ObjectStartOffsetInDataPage() + object_size,
-              allocator->GetCommitPageSize()) -
+              MemoryAllocator::GetCommitPageSize()) -
       MemoryChunkLayout::ObjectStartOffsetInDataPage();
   CHECK_EQ(faked_space->Capacity(), 2 * capacity_per_page);
 }