cppgc: shared-cage: Use dedicated reservations for normal/large pages

The CL splits the Oilpan giga-cage in two 2GB reservations: one for
normal pages and the other for large ones. The split enables fast
page-header lookup (assuming most objects reside on normal pages), which
is needed for:
1) the young generation project, where the remembered set will move to
   pages;
2) the shared-cage project, to find HeapBase* from page-headers.

Bug: v8:12231, chromium:1029379
Change-Id: I4ae9e8a75a307ed0dff9a2ec4f1247b80e17ebd9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3688519
Auto-Submit: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80950}

include/cppgc/internal/api-constants.h

@@ -37,6 +37,9 @@ static constexpr size_t kLargeObjectSizeThreshold = kPageSize / 2;
 #if defined(CPPGC_CAGED_HEAP)
 constexpr size_t kCagedHeapReservationSize = static_cast<size_t>(4) * kGB;
 constexpr size_t kCagedHeapReservationAlignment = kCagedHeapReservationSize;
+
+constexpr size_t kCagedHeapNormalPageReservationSize =
+    kCagedHeapReservationSize / 2;
 #endif
 
 static constexpr size_t kDefaultAlignment = sizeof(void*);

src/heap/cppgc/caged-heap.cc

@@ -16,6 +16,7 @@
 #include "src/base/platform/platform.h"
 #include "src/heap/cppgc/caged-heap.h"
 #include "src/heap/cppgc/globals.h"
+#include "src/heap/cppgc/heap-page.h"
 #include "src/heap/cppgc/member.h"
 
 namespace cppgc {
@@ -25,6 +26,8 @@ static_assert(api_constants::kCagedHeapReservationSize ==
               kCagedHeapReservationSize);
 static_assert(api_constants::kCagedHeapReservationAlignment ==
               kCagedHeapReservationAlignment);
+static_assert(api_constants::kCagedHeapNormalPageReservationSize ==
+              kCagedHeapNormalPageReservationSize);
 
 namespace {
 
@@ -78,9 +81,20 @@ CagedHeap::CagedHeap(HeapBase& heap_base, PageAllocator& platform_allocator)
       caged_heap_start -
       reinterpret_cast<CagedAddress>(reserved_area_.address());
 
-  bounded_allocator_ = std::make_unique<v8::base::BoundedPageAllocator>(
+  normal_page_bounded_allocator_ = std::make_unique<
+      v8::base::BoundedPageAllocator>(
       &platform_allocator, caged_heap_start,
-      reserved_area_.size() - local_data_size_with_padding, kPageSize,
+      kCagedHeapNormalPageReservationSize - local_data_size_with_padding,
+      kPageSize,
+      v8::base::PageInitializationMode::kAllocatedPagesMustBeZeroInitialized,
+      v8::base::PageFreeingMode::kMakeInaccessible);
+
+  large_page_bounded_allocator_ = std::make_unique<
+      v8::base::BoundedPageAllocator>(
+      &platform_allocator,
+      reinterpret_cast<uintptr_t>(reserved_area_.address()) +
+          kCagedHeapNormalPageReservationSize,
+      kCagedHeapNormalPageReservationSize, kPageSize,
       v8::base::PageInitializationMode::kAllocatedPagesMustBeZeroInitialized,
       v8::base::PageFreeingMode::kMakeInaccessible);
 }
@@ -99,5 +113,37 @@ void CagedHeap::EnableGenerationalGC() {
 }
 #endif  // defined(CPPGC_YOUNG_GENERATION)
 
+void CagedHeap::NotifyLargePageCreated(LargePage* page) {
+  DCHECK(page);
+  auto result = large_pages_.insert(page);
+  USE(result);
+  DCHECK(result.second);
+}
+
+void CagedHeap::NotifyLargePageDestroyed(LargePage* page) {
+  DCHECK(page);
+  auto size = large_pages_.erase(page);
+  USE(size);
+  DCHECK_EQ(1u, size);
+}
+
+BasePage* CagedHeap::LookupPageFromInnerPointer(void* ptr) const {
+  DCHECK(IsOnHeap(ptr));
+  if (V8_LIKELY(IsWithinNormalPageReservation(ptr))) {
+    return NormalPage::FromPayload(ptr);
+  } else {
+    return LookupLargePageFromInnerPointer(ptr);
+  }
+}
+
+LargePage* CagedHeap::LookupLargePageFromInnerPointer(void* ptr) const {
+  auto it = large_pages_.upper_bound(static_cast<LargePage*>(ptr));
+  DCHECK_NE(large_pages_.begin(), it);
+  auto* page = *std::next(it, -1);
+  DCHECK(page);
+  DCHECK(page->PayloadContains(static_cast<ConstAddress>(ptr)));
+  return page;
+}
+
 }  // namespace internal
 }  // namespace cppgc

src/heap/cppgc/caged-heap.h

@@ -7,6 +7,7 @@
 
 #include <limits>
 #include <memory>
+#include <set>
 
 #include "include/cppgc/platform.h"
 #include "src/base/bounded-page-allocator.h"
@@ -18,6 +19,8 @@ namespace internal {
 
 struct CagedHeapLocalData;
 class HeapBase;
+class BasePage;
+class LargePage;
 
 class CagedHeap final {
  public:
@@ -37,6 +40,10 @@ class CagedHeap final {
            ~(kCagedHeapReservationAlignment - 1);
   }
 
+  static bool IsWithinNormalPageReservation(const void* address) {
+    return OffsetFromAddress(address) < kCagedHeapNormalPageReservationSize;
+  }
+
   CagedHeap(HeapBase& heap, PageAllocator& platform_allocator);
   ~CagedHeap();
 
@@ -47,8 +54,24 @@ class CagedHeap final {
   void EnableGenerationalGC();
 #endif  // defined(CPPGC_YOUNG_GENERATION)
 
-  AllocatorType& allocator() { return *bounded_allocator_; }
-  const AllocatorType& allocator() const { return *bounded_allocator_; }
+  AllocatorType& normal_page_allocator() {
+    return *normal_page_bounded_allocator_;
+  }
+  const AllocatorType& normal_page_allocator() const {
+    return *normal_page_bounded_allocator_;
+  }
+
+  AllocatorType& large_page_allocator() {
+    return *large_page_bounded_allocator_;
+  }
+  const AllocatorType& large_page_allocator() const {
+    return *large_page_bounded_allocator_;
+  }
+
+  void NotifyLargePageCreated(LargePage* page);
+  void NotifyLargePageDestroyed(LargePage* page);
+
+  BasePage* LookupPageFromInnerPointer(void* ptr) const;
 
   CagedHeapLocalData& local_data() {
     return *static_cast<CagedHeapLocalData*>(reserved_area_.address());
@@ -65,8 +88,12 @@ class CagedHeap final {
   void* base() const { return reserved_area_.address(); }
 
  private:
+  LargePage* LookupLargePageFromInnerPointer(void* ptr) const;
+
   const VirtualMemory reserved_area_;
-  std::unique_ptr<AllocatorType> bounded_allocator_;
+  std::unique_ptr<AllocatorType> normal_page_bounded_allocator_;
+  std::unique_ptr<AllocatorType> large_page_bounded_allocator_;
+  std::set<LargePage*> large_pages_;
 };
 
 }  // namespace internal

src/heap/cppgc/globals.h

@@ -75,6 +75,11 @@ constexpr size_t kFreeListEntrySize = 2 * sizeof(uintptr_t);
 
 constexpr size_t kCagedHeapReservationSize = static_cast<size_t>(4) * kGB;
 constexpr size_t kCagedHeapReservationAlignment = kCagedHeapReservationSize;
+// TODO(v8:12231): To reduce OOM probability, instead of the fixed-size
+// reservation consider to use a moving needle implementation or simply
+// calibrating this 2GB/2GB split.
+constexpr size_t kCagedHeapNormalPageReservationSize =
+    kCagedHeapReservationSize / 2;
 
 }  // namespace internal
 }  // namespace cppgc

src/heap/cppgc/heap-base.cc

@@ -66,11 +66,12 @@ HeapBase::HeapBase(
 #endif  // LEAK_SANITIZER
 #if defined(CPPGC_CAGED_HEAP)
       caged_heap_(*this, *page_allocator()),
-      page_backend_(std::make_unique<PageBackend>(caged_heap_.allocator(),
-                                                  *oom_handler_.get())),
+      page_backend_(std::make_unique<PageBackend>(
+          caged_heap_.normal_page_allocator(),
+          caged_heap_.large_page_allocator(), *oom_handler_.get())),
 #else   // !CPPGC_CAGED_HEAP
-      page_backend_(std::make_unique<PageBackend>(*page_allocator(),
-                                                  *oom_handler_.get())),
+      page_backend_(std::make_unique<PageBackend>(
+          *page_allocator(), *page_allocator(), *oom_handler_.get())),
 #endif  // !CPPGC_CAGED_HEAP
       stats_collector_(std::make_unique<StatsCollector>(platform_.get())),
       stack_(std::make_unique<heap::base::Stack>(
@@ -158,7 +159,7 @@ void HeapBase::ResetRememberedSet() {
     return;
   }
 
-  caged_heap().local_data().age_table.Reset(&caged_heap().allocator());
+  caged_heap().local_data().age_table.Reset(page_allocator());
   remembered_set_.Reset();
   return;
 }

src/heap/cppgc/heap-page.cc

@@ -40,8 +40,13 @@ BasePage* BasePage::FromInnerAddress(const HeapBase* heap, void* address) {
 // static
 const BasePage* BasePage::FromInnerAddress(const HeapBase* heap,
                                            const void* address) {
+#if defined(CPPGC_CAGED_HEAP)
+  return heap->caged_heap().LookupPageFromInnerPointer(
+      const_cast<void*>(address));
+#else   // !defined(CPPGC_CAGED_HEAP)
   return reinterpret_cast<const BasePage*>(
       heap->page_backend()->Lookup(static_cast<ConstAddress>(address)));
+#endif  // !defined(CPPGC_CAGED_HEAP)
 }
 
 // static
@@ -231,6 +236,9 @@ LargePage* LargePage::Create(PageBackend& page_backend, LargePageSpace& space,
   void* memory = page_backend.AllocateLargePageMemory(allocation_size);
   LargePage* page = new (memory) LargePage(*heap, space, size);
   page->SynchronizedStore();
+#if defined(CPPGC_CAGED_HEAP)
+  heap->caged_heap().NotifyLargePageCreated(page);
+#endif  // defined(CPPGC_CAGED_HEAP)
   page->heap().stats_collector()->NotifyAllocatedMemory(allocation_size);
   return page;
 }
@@ -238,6 +246,8 @@ LargePage* LargePage::Create(PageBackend& page_backend, LargePageSpace& space,
 // static
 void LargePage::Destroy(LargePage* page) {
   DCHECK(page);
+  HeapBase& heap = page->heap();
+  const size_t payload_size = page->PayloadSize();
 #if DEBUG
   const BaseSpace& space = page->space();
   {
@@ -249,9 +259,11 @@ void LargePage::Destroy(LargePage* page) {
   }
 #endif  // DEBUG
   page->~LargePage();
-  PageBackend* backend = page->heap().page_backend();
-  page->heap().stats_collector()->NotifyFreedMemory(
-      AllocationSize(page->PayloadSize()));
+  PageBackend* backend = heap.page_backend();
+#if defined(CPPGC_CAGED_HEAP)
+  heap.caged_heap().NotifyLargePageDestroyed(page);
+#endif  // defined(CPPGC_CAGED_HEAP)
+  heap.stats_collector()->NotifyFreedMemory(AllocationSize(payload_size));
   backend->FreeLargePageMemory(reinterpret_cast<Address>(page));
 }
 

src/heap/cppgc/page-memory.cc

@@ -186,9 +186,12 @@ std::pair<NormalPageMemoryRegion*, Address> NormalPageMemoryPool::Take(
   return pair;
 }
 
-PageBackend::PageBackend(PageAllocator& allocator,
+PageBackend::PageBackend(PageAllocator& normal_page_allocator,
+                         PageAllocator& large_page_allocator,
                          FatalOutOfMemoryHandler& oom_handler)
-    : allocator_(allocator), oom_handler_(oom_handler) {}
+    : normal_page_allocator_(normal_page_allocator),
+      large_page_allocator_(large_page_allocator),
+      oom_handler_(oom_handler) {}
 
 PageBackend::~PageBackend() = default;
 
@@ -196,8 +199,8 @@ Address PageBackend::AllocateNormalPageMemory(size_t bucket) {
   v8::base::MutexGuard guard(&mutex_);
   std::pair<NormalPageMemoryRegion*, Address> result = page_pool_.Take(bucket);
   if (!result.first) {
-    auto pmr =
-        std::make_unique<NormalPageMemoryRegion>(allocator_, oom_handler_);
+    auto pmr = std::make_unique<NormalPageMemoryRegion>(normal_page_allocator_,
+                                                        oom_handler_);
     for (size_t i = 0; i < NormalPageMemoryRegion::kNumPageRegions; ++i) {
       page_pool_.Add(bucket, pmr.get(),
                      pmr->GetPageMemory(i).writeable_region().base());
@@ -221,10 +224,10 @@ void PageBackend::FreeNormalPageMemory(size_t bucket, Address writeable_base) {
 
 Address PageBackend::AllocateLargePageMemory(size_t size) {
   v8::base::MutexGuard guard(&mutex_);
-  auto pmr =
-      std::make_unique<LargePageMemoryRegion>(allocator_, oom_handler_, size);
+  auto pmr = std::make_unique<LargePageMemoryRegion>(large_page_allocator_,
+                                                     oom_handler_, size);
   const PageMemory pm = pmr->GetPageMemory();
-  Unprotect(allocator_, oom_handler_, pm);
+  Unprotect(large_page_allocator_, oom_handler_, pm);
   page_memory_region_tree_.Add(pmr.get());
   large_page_memory_regions_.insert(std::make_pair(pmr.get(), std::move(pmr)));
   return pm.writeable_region().base();

src/heap/cppgc/page-memory.h

@@ -198,7 +198,8 @@ class V8_EXPORT_PRIVATE NormalPageMemoryPool final {
 // regions alive.
 class V8_EXPORT_PRIVATE PageBackend final {
  public:
-  PageBackend(PageAllocator&, FatalOutOfMemoryHandler&);
+  PageBackend(PageAllocator& normal_page_allocator,
+              PageAllocator& large_page_allocator, FatalOutOfMemoryHandler&);
   ~PageBackend();
 
   // Allocates a normal page from the backend.
@@ -230,7 +231,8 @@ class V8_EXPORT_PRIVATE PageBackend final {
  private:
   // Guards against concurrent uses of `Lookup()`.
   mutable v8::base::Mutex mutex_;
-  PageAllocator& allocator_;
+  PageAllocator& normal_page_allocator_;
+  PageAllocator& large_page_allocator_;
   FatalOutOfMemoryHandler& oom_handler_;
   NormalPageMemoryPool page_pool_;
   PageMemoryRegionTree page_memory_region_tree_;

test/unittests/heap/cppgc/page-memory-unittest.cc

@@ -269,7 +269,7 @@ TEST(NormalPageMemoryPool, AddTakeNotFoundDifferentBucket) {
 TEST(PageBackendTest, AllocateNormalUsesPool) {
   v8::base::PageAllocator allocator;
   FatalOutOfMemoryHandler oom_handler;
-  PageBackend backend(allocator, oom_handler);
+  PageBackend backend(allocator, allocator, oom_handler);
   constexpr size_t kBucket = 0;
   Address writeable_base1 = backend.AllocateNormalPageMemory(kBucket);
   EXPECT_NE(nullptr, writeable_base1);
@@ -282,7 +282,7 @@ TEST(PageBackendTest, AllocateNormalUsesPool) {
 TEST(PageBackendTest, AllocateLarge) {
   v8::base::PageAllocator allocator;
   FatalOutOfMemoryHandler oom_handler;
-  PageBackend backend(allocator, oom_handler);
+  PageBackend backend(allocator, allocator, oom_handler);
   Address writeable_base1 = backend.AllocateLargePageMemory(13731);
   EXPECT_NE(nullptr, writeable_base1);
   Address writeable_base2 = backend.AllocateLargePageMemory(9478);
@@ -295,7 +295,7 @@ TEST(PageBackendTest, AllocateLarge) {
 TEST(PageBackendTest, LookupNormal) {
   v8::base::PageAllocator allocator;
   FatalOutOfMemoryHandler oom_handler;
-  PageBackend backend(allocator, oom_handler);
+  PageBackend backend(allocator, allocator, oom_handler);
   constexpr size_t kBucket = 0;
   Address writeable_base = backend.AllocateNormalPageMemory(kBucket);
   if (kGuardPageSize) {
@@ -316,7 +316,7 @@ TEST(PageBackendTest, LookupNormal) {
 TEST(PageBackendTest, LookupLarge) {
   v8::base::PageAllocator allocator;
   FatalOutOfMemoryHandler oom_handler;
-  PageBackend backend(allocator, oom_handler);
+  PageBackend backend(allocator, allocator, oom_handler);
   constexpr size_t kSize = 7934;
   Address writeable_base = backend.AllocateLargePageMemory(kSize);
   if (kGuardPageSize) {
@@ -332,7 +332,7 @@ TEST(PageBackendDeathTest, DestructingBackendDestroysPageMemory) {
   FatalOutOfMemoryHandler oom_handler;
   Address base;
   {
-    PageBackend backend(allocator, oom_handler);
+    PageBackend backend(allocator, allocator, oom_handler);
     constexpr size_t kBucket = 0;
     base = backend.AllocateNormalPageMemory(kBucket);
   }