Move memory layout and common methods of AlignedHeapSegment to a base…

… class (#1510)

Summary:

The large heap segment type should have the same storage layout as
current AlignedHeapSegment, and share a few common methods. Abstract
these to a base class, and make both FixedSizeHeapSegment and
JumboHeapSegment inherit from the base type.

Differential Revision: D61675022

include/hermes/VM/CardTableNC.h

@@ -23,7 +23,7 @@ namespace vm {
 
 /// The card table optimizes young gen collections by restricting the amount of
 /// heap belonging to the old gen that must be scanned.  The card table expects
-/// to be constructed inside an AlignedHeapSegment's storage, at some position
+/// to be constructed inside an FixedSizeHeapSegment's storage, at some position
 /// before the allocation region, and covers the extent of that storage's
 /// memory.
 ///

include/hermes/VM/GCBase.h

@@ -226,7 +226,7 @@ enum XorPtrKeyID {
 ///   Return the maximum amount of bytes holdable by this heap.
 ///     gcheapsize_t max() const;
 ///   Return the total amount of bytes of storage this GC will require.
-///   This will be a multiple of AlignedHeapSegment::storageSize().
+///   This will be a multiple of FixedSizeHeapSegment::storageSize().
 ///     gcheapsize_t storageFootprint() const;
 ///
 class GCBase {

include/hermes/VM/HadesGC.h

@@ -76,7 +76,7 @@ class HadesGC final : public GCBase {
   static constexpr uint32_t maxAllocationSizeImpl() {
     // The largest allocation allowable in Hades is the max size a single
     // segment supports.
-    return AlignedHeapSegment::maxSize();
+    return FixedSizeHeapSegment::maxSize();
   }
 
   static constexpr uint32_t minAllocationSizeImpl() {
@@ -297,7 +297,7 @@ class HadesGC final : public GCBase {
 
   /// \return true if the pointer lives in the young generation.
   bool inYoungGen(const void *p) const override {
-    return youngGen_.lowLim() == AlignedHeapSegment::storageStart(p);
+    return youngGen_.lowLim() == FixedSizeHeapSegment::storageStart(p);
   }
   bool inYoungGen(CompressedPointer p) const {
     return p.getSegmentStart() == youngGenCP_;
@@ -361,34 +361,34 @@ class HadesGC final : public GCBase {
   /// Call \p callback on every non-freelist cell allocated in this segment.
   template <typename CallbackFunction>
   static void forAllObjsInSegment(
-      AlignedHeapSegment &seg,
+      FixedSizeHeapSegment &seg,
       CallbackFunction callback);
   /// Only call the callback on cells without forwarding pointers.
   template <typename CallbackFunction>
   static void forCompactedObjsInSegment(
-      AlignedHeapSegment &seg,
+      FixedSizeHeapSegment &seg,
       CallbackFunction callback,
       PointerBase &base);
 
   class OldGen final {
    public:
     explicit OldGen(HadesGC &gc);
 
-    std::deque<AlignedHeapSegment>::iterator begin();
-    std::deque<AlignedHeapSegment>::iterator end();
-    std::deque<AlignedHeapSegment>::const_iterator begin() const;
-    std::deque<AlignedHeapSegment>::const_iterator end() const;
+    std::deque<FixedSizeHeapSegment>::iterator begin();
+    std::deque<FixedSizeHeapSegment>::iterator end();
+    std::deque<FixedSizeHeapSegment>::const_iterator begin() const;
+    std::deque<FixedSizeHeapSegment>::const_iterator end() const;
 
     size_t numSegments() const;
 
-    AlignedHeapSegment &operator[](size_t i);
+    FixedSizeHeapSegment &operator[](size_t i);
 
     /// Take ownership of the given segment.
-    void addSegment(AlignedHeapSegment seg);
+    void addSegment(FixedSizeHeapSegment seg);
 
     /// Remove the last segment from the OG.
     /// \return the segment that was removed.
-    AlignedHeapSegment popSegment();
+    FixedSizeHeapSegment popSegment();
 
     /// Indicate that OG should target having a size of \p targetSizeBytes.
     void setTargetSizeBytes(size_t targetSizeBytes);
@@ -507,7 +507,7 @@ class HadesGC final : public GCBase {
     static constexpr size_t kMinSizeForLargeBlock = 1
         << kLogMinSizeForLargeBlock;
     static constexpr size_t kNumLargeFreelistBuckets =
-        llvh::detail::ConstantLog2<AlignedHeapSegment::maxSize()>::value -
+        llvh::detail::ConstantLog2<FixedSizeHeapSegment::maxSize()>::value -
         kLogMinSizeForLargeBlock + 1;
     static constexpr size_t kNumFreelistBuckets =
         kNumSmallFreelistBuckets + kNumLargeFreelistBuckets;
@@ -578,7 +578,7 @@ class HadesGC final : public GCBase {
 
     /// Use a std::deque instead of a std::vector so that references into it
     /// remain valid across a push_back.
-    std::deque<AlignedHeapSegment> segments_;
+    std::deque<FixedSizeHeapSegment> segments_;
 
     /// See \c targetSizeBytes() above.
     ExponentialMovingAverage targetSizeBytes_{0, 0};
@@ -660,9 +660,9 @@ class HadesGC final : public GCBase {
   /// Keeps the storage provider alive until after the GC is fully destructed.
   std::shared_ptr<StorageProvider> provider_;
 
-  /// youngGen is a bump-pointer space, so it can re-use AlignedHeapSegment.
+  /// youngGen is a bump-pointer space, so it can re-use FixedSizeHeapSegment.
   /// Protected by gcMutex_.
-  AlignedHeapSegment youngGen_;
+  FixedSizeHeapSegment youngGen_;
   AssignableCompressedPointer youngGenCP_;
 
   /// List of cells in YG that have finalizers. Iterate through this to clean
@@ -672,7 +672,7 @@ class HadesGC final : public GCBase {
 
   /// Since YG collection times are the primary driver of pause times, it is
   /// useful to have a knob to reduce the effective size of the YG. This number
-  /// is the fraction of AlignedHeapSegment::maxSize() that we should use for
+  /// is the fraction of FixedSizeHeapSegment::maxSize() that we should use for
   /// the YG.. Note that we only set the YG size using this at the end of the
   /// first real YG, since doing it for direct promotions would waste OG memory
   /// without a pause time benefit.
@@ -772,7 +772,7 @@ class HadesGC final : public GCBase {
     /// \return true if the pointer lives in the segment that is being marked or
     /// evacuated for compaction.
     bool contains(const void *p) const {
-      return start == AlignedHeapSegment::storageStart(p);
+      return start == FixedSizeHeapSegment::storageStart(p);
     }
     bool contains(CompressedPointer p) const {
       return p.getSegmentStart() == startCP;
@@ -781,7 +781,7 @@ class HadesGC final : public GCBase {
     /// \return true if the pointer lives in the segment that is currently being
     /// evacuated for compaction.
     bool evacContains(const void *p) const {
-      return evacStart == AlignedHeapSegment::storageStart(p);
+      return evacStart == FixedSizeHeapSegment::storageStart(p);
     }
     bool evacContains(CompressedPointer p) const {
       return p.getSegmentStart() == evacStartCP;
@@ -829,7 +829,7 @@ class HadesGC final : public GCBase {
     /// The segment being compacted. This should be removed from the OG right
     /// after it is identified, and freed entirely once the compaction is
     /// complete.
-    std::shared_ptr<AlignedHeapSegment> segment;
+    std::shared_ptr<FixedSizeHeapSegment> segment;
   } compactee_;
 
   /// The number of compactions this GC has performed.
@@ -964,7 +964,7 @@ class HadesGC final : public GCBase {
   template <bool CompactionEnabled>
   void scanDirtyCardsForSegment(
       EvacAcceptor<CompactionEnabled> &acceptor,
-      AlignedHeapSegment &segment);
+      FixedSizeHeapSegment &segment);
 
   /// Find all pointers from OG into the YG/compactee during a YG collection.
   /// This is done quickly through use of write barriers that detect the
@@ -1011,19 +1011,19 @@ class HadesGC final : public GCBase {
   uint64_t heapFootprint() const;
 
   /// Accessor for the YG.
-  AlignedHeapSegment &youngGen() {
+  FixedSizeHeapSegment &youngGen() {
     return youngGen_;
   }
-  const AlignedHeapSegment &youngGen() const {
+  const FixedSizeHeapSegment &youngGen() const {
     return youngGen_;
   }
 
   /// Create a new segment (to be used by either YG or OG).
-  llvh::ErrorOr<AlignedHeapSegment> createSegment();
+  llvh::ErrorOr<FixedSizeHeapSegment> createSegment();
 
   /// Set a given segment as the YG segment.
   /// \return the previous YG segment.
-  AlignedHeapSegment setYoungGen(AlignedHeapSegment seg);
+  FixedSizeHeapSegment setYoungGen(FixedSizeHeapSegment seg);
 
   /// Get/set the current number of external bytes used by the YG.
   size_t getYoungGenExternalBytes() const;
@@ -1048,7 +1048,7 @@ class HadesGC final : public GCBase {
   /// \param extraName append this to the name of the segment. Must be
   ///   non-empty.
   void addSegmentExtentToCrashManager(
-      const AlignedHeapSegment &seg,
+      const FixedSizeHeapSegment &seg,
       const std::string &extraName);
 
   /// Deletes a segment from the CrashManager's custom data.

include/hermes/VM/HeapRuntime.h

@@ -40,7 +40,8 @@ class HeapRuntime {
     if (!ptrOrError)
       hermes_fatal("Cannot initialize Runtime storage.", ptrOrError.getError());
     static_assert(
-        sizeof(RT) < AlignedHeapSegment::storageSize(), "Segments too small.");
+        sizeof(RT) < FixedSizeHeapSegment::storageSize(),
+        "Segments too small.");
     runtime_ = static_cast<RT *>(*ptrOrError);
   }
 

include/hermes/VM/StorageProvider.h

@@ -43,13 +43,14 @@ class StorageProvider {
   }
   /// Create a new segment memory space and give this memory the name \p name.
   /// \return A pointer to a block of memory that has
-  /// AlignedHeapSegment::storageSize() bytes, and is aligned on
-  /// AlignedHeapSegment::storageSize().
+  /// FixedSizeHeapSegment::storageSize() bytes, and is aligned on
+  /// FixedSizeHeapSegment::storageSize().
   llvh::ErrorOr<void *> newStorage(const char *name);
 
   /// Delete the given segment's memory space, and make it available for re-use.
   /// \post Nothing in the range [storage, storage +
-  /// AlignedHeapSegment::storageSize()) is valid memory to be read or written.
+  /// FixedSizeHeapSegment::storageSize()) is valid memory to be read or
+  /// written.
   void deleteStorage(void *storage);
 
   /// The number of storages this provider has allocated in its lifetime.

lib/VM/LimitedStorageProvider.cpp

@@ -14,10 +14,10 @@ namespace hermes {
 namespace vm {
 
 llvh::ErrorOr<void *> LimitedStorageProvider::newStorageImpl(const char *name) {
-  if (limit_ < AlignedHeapSegment::storageSize()) {
+  if (limit_ < FixedSizeHeapSegment::storageSize()) {
     return make_error_code(OOMError::TestVMLimitReached);
   }
-  limit_ -= AlignedHeapSegment::storageSize();
+  limit_ -= FixedSizeHeapSegment::storageSize();
   return delegate_->newStorage(name);
 }
 
@@ -26,7 +26,7 @@ void LimitedStorageProvider::deleteStorageImpl(void *storage) {
     return;
   }
   delegate_->deleteStorage(storage);
-  limit_ += AlignedHeapSegment::storageSize();
+  limit_ += FixedSizeHeapSegment::storageSize();
 }
 
 } // namespace vm

lib/VM/Runtime.cpp

@@ -159,7 +159,7 @@ std::shared_ptr<Runtime> Runtime::create(const RuntimeConfig &runtimeConfig) {
   uint64_t maxHeapSize = runtimeConfig.getGCConfig().getMaxHeapSize();
   // Allow some extra segments for the runtime, and as a buffer for the GC.
   uint64_t providerSize = std::min<uint64_t>(
-      1ULL << 32, maxHeapSize + AlignedHeapSegment::storageSize() * 4);
+      1ULL << 32, maxHeapSize + FixedSizeHeapSegment::storageSize() * 4);
   std::shared_ptr<StorageProvider> sp =
       StorageProvider::contiguousVAProvider(providerSize);
   auto rt = HeapRuntime<Runtime>::create(sp);
@@ -252,7 +252,6 @@ void RuntimeBase::registerHeapSegment(unsigned idx, void *lowLim) {
       reinterpret_cast<char *>(lowLim) - (idx << AlignedHeapSegment::kLogSize);
   segmentMap[idx] = bias;
 #endif
-  assert(lowLim == AlignedHeapSegment::storageStart(lowLim) && "Precondition");
   AlignedHeapSegment::setSegmentIndexFromStart(lowLim, idx);
 }
 

lib/VM/StorageProvider.cpp

@@ -57,12 +57,12 @@ namespace {
 
 bool isAligned(void *p) {
   return (reinterpret_cast<uintptr_t>(p) &
-          (AlignedHeapSegment::storageSize() - 1)) == 0;
+          (FixedSizeHeapSegment::storageSize() - 1)) == 0;
 }
 
 char *alignAlloc(void *p) {
   return reinterpret_cast<char *>(llvh::alignTo(
-      reinterpret_cast<uintptr_t>(p), AlignedHeapSegment::storageSize()));
+      reinterpret_cast<uintptr_t>(p), FixedSizeHeapSegment::storageSize()));
 }
 
 void *getMmapHint() {
@@ -85,9 +85,9 @@ class VMAllocateStorageProvider final : public StorageProvider {
 class ContiguousVAStorageProvider final : public StorageProvider {
  public:
   ContiguousVAStorageProvider(size_t size)
-      : size_(llvh::alignTo<AlignedHeapSegment::storageSize()>(size)) {
+      : size_(llvh::alignTo<FixedSizeHeapSegment::storageSize()>(size)) {
     auto result = oscompat::vm_reserve_aligned(
-        size_, AlignedHeapSegment::storageSize(), getMmapHint());
+        size_, FixedSizeHeapSegment::storageSize(), getMmapHint());
     if (!result)
       hermes_fatal("Contiguous storage allocation failed.", result.getError());
     level_ = start_ = static_cast<char *>(*result);
@@ -104,26 +104,27 @@ class ContiguousVAStorageProvider final : public StorageProvider {
       freelist_.pop_back();
     } else if (level_ < start_ + size_) {
       storage =
-          std::exchange(level_, level_ + AlignedHeapSegment::storageSize());
+          std::exchange(level_, level_ + FixedSizeHeapSegment::storageSize());
     } else {
       return make_error_code(OOMError::MaxStorageReached);
     }
-    auto res = oscompat::vm_commit(storage, AlignedHeapSegment::storageSize());
+    auto res =
+        oscompat::vm_commit(storage, FixedSizeHeapSegment::storageSize());
     if (res) {
-      oscompat::vm_name(storage, AlignedHeapSegment::storageSize(), name);
+      oscompat::vm_name(storage, FixedSizeHeapSegment::storageSize(), name);
     }
     return res;
   }
 
   void deleteStorageImpl(void *storage) override {
     assert(
         !llvh::alignmentAdjustment(
-            storage, AlignedHeapSegment::storageSize()) &&
+            storage, FixedSizeHeapSegment::storageSize()) &&
         "Storage not aligned");
     assert(storage >= start_ && storage < level_ && "Storage not in region");
     oscompat::vm_name(
-        storage, AlignedHeapSegment::storageSize(), kFreeRegionName);
-    oscompat::vm_uncommit(storage, AlignedHeapSegment::storageSize());
+        storage, FixedSizeHeapSegment::storageSize(), kFreeRegionName);
+    oscompat::vm_uncommit(storage, FixedSizeHeapSegment::storageSize());
     freelist_.push_back(storage);
   }
 
@@ -149,11 +150,11 @@ class MallocStorageProvider final : public StorageProvider {
 
 llvh::ErrorOr<void *> VMAllocateStorageProvider::newStorageImpl(
     const char *name) {
-  assert(AlignedHeapSegment::storageSize() % oscompat::page_size() == 0);
+  assert(FixedSizeHeapSegment::storageSize() % oscompat::page_size() == 0);
   // Allocate the space, hoping it will be the correct alignment.
   auto result = oscompat::vm_allocate_aligned(
-      AlignedHeapSegment::storageSize(),
-      AlignedHeapSegment::storageSize(),
+      FixedSizeHeapSegment::storageSize(),
+      FixedSizeHeapSegment::storageSize(),
       getMmapHint());
   if (!result) {
     return result;
@@ -162,25 +163,25 @@ llvh::ErrorOr<void *> VMAllocateStorageProvider::newStorageImpl(
   assert(isAligned(mem));
   (void)&isAligned;
 #ifdef HERMESVM_ALLOW_HUGE_PAGES
-  oscompat::vm_hugepage(mem, AlignedHeapSegment::storageSize());
+  oscompat::vm_hugepage(mem, FixedSizeHeapSegment::storageSize());
 #endif
 
   // Name the memory region on platforms that support naming.
-  oscompat::vm_name(mem, AlignedHeapSegment::storageSize(), name);
+  oscompat::vm_name(mem, FixedSizeHeapSegment::storageSize(), name);
   return mem;
 }
 
 void VMAllocateStorageProvider::deleteStorageImpl(void *storage) {
   if (!storage) {
     return;
   }
-  oscompat::vm_free_aligned(storage, AlignedHeapSegment::storageSize());
+  oscompat::vm_free_aligned(storage, FixedSizeHeapSegment::storageSize());
 }
 
 llvh::ErrorOr<void *> MallocStorageProvider::newStorageImpl(const char *name) {
   // name is unused, can't name malloc memory.
   (void)name;
-  void *mem = checkedMalloc2(AlignedHeapSegment::storageSize(), 2u);
+  void *mem = checkedMalloc2(FixedSizeHeapSegment::storageSize(), 2u);
   void *lowLim = alignAlloc(mem);
   assert(isAligned(lowLim) && "New storage should be aligned");
   lowLimToAllocHandle_[lowLim] = mem;