Add support of allocating different sizes of storage in StorageProvid…

…er (facebook#1504)

Summary:
Pull Request resolved: facebook#1504

Large segment needs to be backed by a large storage size.
StorageProvider currently always allocate fixed size of storage
determined by HERMESVM_LOG_HEAP_SEGMENT_SIZE.

This diffs adds support of allocating larger storage with below
changes:
1. `newStorage()` and `deleteStorage()` takes additional `sz` parameter.
2. For `MallocStorageProvider` and `VMAllocateStorageProvider`, simply
change the previous fixed storage size to passed in `sz`.
3. For `ContiguousVAStorageProvider`, use a BitVector to manage
allocations and deallocations. This can be improved later if we observe
fragmentations.

The support of enabling different sizes of heap segment will be added
later.

Differential Revision: D61676721

include/hermes/Support/ErrorHandling.h

@@ -37,6 +37,8 @@ enum class OOMError : int {
   Effective,
   // When an allocation is requested that is larger than a heap segment.
   SuperSegmentAlloc,
+  // When requesting a segment that is too large to create.
+  TooLargeSegmentRequest,
   // When a CopyableVector's capacity overflows what an integer can hold.
   CopyableVectorCapacityIntegerOverflow,
   // This happens when a unit test attempts to allocate more storages

include/hermes/VM/HeapRuntime.h

@@ -22,7 +22,7 @@ class HeapRuntime {
  public:
   ~HeapRuntime() {
     runtime_->~RT();
-    sp_->deleteStorage(runtime_);
+    sp_->deleteStorage(runtime_, kHeapRuntimeStorageSize);
   }
 
   /// Allocate a segment and create an aliased shared_ptr that points to the
@@ -36,17 +36,16 @@ class HeapRuntime {
 
  private:
   HeapRuntime(std::shared_ptr<StorageProvider> sp) : sp_{std::move(sp)} {
-    auto ptrOrError = sp_->newStorage("hermes-rt");
+    auto ptrOrError = sp_->newStorage(kHeapRuntimeStorageSize, "hermes-rt");
     if (!ptrOrError)
       hermes_fatal("Cannot initialize Runtime storage.", ptrOrError.getError());
-    static_assert(
-        sizeof(RT) < FixedSizeHeapSegment::storageSize(),
-        "Segments too small.");
+    static_assert(sizeof(RT) < kHeapRuntimeStorageSize, "Segments too small.");
     runtime_ = static_cast<RT *>(*ptrOrError);
   }
 
   std::shared_ptr<StorageProvider> sp_;
   RT *runtime_;
+  static constexpr size_t kHeapRuntimeStorageSize = FixedSizeHeapSegment::kSize;
 };
 } // namespace vm
 } // namespace hermes

include/hermes/VM/LimitedStorageProvider.h

@@ -29,9 +29,9 @@ class LimitedStorageProvider final : public StorageProvider {
       : delegate_(std::move(provider)), limit_(limit) {}
 
  protected:
-  llvh::ErrorOr<void *> newStorageImpl(const char *name) override;
+  llvh::ErrorOr<void *> newStorageImpl(size_t sz, const char *name) override;
 
-  void deleteStorageImpl(void *storage) override;
+  void deleteStorageImpl(void *storage, size_t sz) override;
 };
 
 } // namespace vm

include/hermes/VM/StorageProvider.h

@@ -37,21 +37,17 @@ class StorageProvider {
 
   /// @}
 
-  /// Create a new segment memory space.
-  llvh::ErrorOr<void *> newStorage() {
-    return newStorage(nullptr);
-  }
-  /// Create a new segment memory space and give this memory the name \p name.
-  /// \return A pointer to a block of memory that has
-  /// FixedSizeHeapSegment::storageSize() bytes, and is aligned on
-  /// FixedSizeHeapSegment::storageSize().
-  llvh::ErrorOr<void *> newStorage(const char *name);
+  /// \return A pointer to a block of memory that has \p sz bytes, and is
+  /// aligned on AlignedHeapSegment::kSegmentUnitSize. Note that \p sz must
+  /// be non-zero and equals to a multiple of
+  /// AlignedHeapSegment::kSegmentUnitSize.
+  llvh::ErrorOr<void *> newStorage(size_t sz, const char *name = nullptr);
 
   /// Delete the given segment's memory space, and make it available for re-use.
-  /// \post Nothing in the range [storage, storage +
-  /// FixedSizeHeapSegment::storageSize()) is valid memory to be read or
-  /// written.
-  void deleteStorage(void *storage);
+  /// Note that \p sz must be the same as used to allocating \p storage.
+  /// \post Nothing in the range [storage, storage + sz) is valid memory to be
+  /// read or written.
+  void deleteStorage(void *storage, size_t sz);
 
   /// The number of storages this provider has allocated in its lifetime.
   size_t numSucceededAllocs() const;
@@ -68,8 +64,12 @@ class StorageProvider {
   size_t numLiveAllocs() const;
 
  protected:
-  virtual llvh::ErrorOr<void *> newStorageImpl(const char *name) = 0;
-  virtual void deleteStorageImpl(void *storage) = 0;
+  /// \pre \p sz is non-zero and equal to a multiple of
+  /// AlignedHeapSegment::kSegmentUnitSize.
+  virtual llvh::ErrorOr<void *> newStorageImpl(size_t sz, const char *name) = 0;
+  /// \pre \p sz is non-zero and equal to a multiple of
+  /// AlignedHeapSegment::kSegmentUnitSize.
+  virtual void deleteStorageImpl(void *storage, size_t sz) = 0;
 
  private:
   size_t numSucceededAllocs_{0};

lib/Support/ErrorHandling.cpp

@@ -29,6 +29,8 @@ const std::error_category &oom_category() {
           return "Effective OOM";
         case OOMError::SuperSegmentAlloc:
           return "Allocation occurred that was larger than a heap segment";
+        case OOMError::TooLargeSegmentRequest:
+          return "Requesting a heap segment that is too large to create";
         case OOMError::CopyableVectorCapacityIntegerOverflow:
           return "CopyableVector capacity integer overflow";
         case OOMError::TestVMLimitReached:

lib/VM/LimitedStorageProvider.cpp

@@ -13,20 +13,22 @@
 namespace hermes {
 namespace vm {
 
-llvh::ErrorOr<void *> LimitedStorageProvider::newStorageImpl(const char *name) {
+llvh::ErrorOr<void *> LimitedStorageProvider::newStorageImpl(
+    size_t sz,
+    const char *name) {
   if (limit_ < FixedSizeHeapSegment::storageSize()) {
     return make_error_code(OOMError::TestVMLimitReached);
   }
-  limit_ -= FixedSizeHeapSegment::storageSize();
-  return delegate_->newStorage(name);
+  limit_ -= sz;
+  return delegate_->newStorage(sz, name);
 }
 
-void LimitedStorageProvider::deleteStorageImpl(void *storage) {
+void LimitedStorageProvider::deleteStorageImpl(void *storage, size_t sz) {
   if (!storage) {
     return;
   }
-  delegate_->deleteStorage(storage);
-  limit_ += FixedSizeHeapSegment::storageSize();
+  delegate_->deleteStorage(storage, sz);
+  limit_ += sz;
 }
 
 } // namespace vm