[scudo][standalone] Secondary & general other improvements

Summary:
This CL changes multiple things to improve performance (notably on
Android).We introduce a cache class for the Secondary that is taking
care of this mechanism now.

The changes:
- change the Secondary "freelist" to an array. By keeping free secondary
  blocks linked together through their headers, we were keeping a page
  per block, which isn't great. Also we know touch less pages when
  walking the new "freelist".
- fix an issue with the freelist getting full: if the pattern is an ever
  increasing size malloc then free, the freelist would fill up and
  entries would not be used. So now we empty the list if we get to many
  "full" events;
- use the global release to os interval option for the secondary: it
  was too costly to release all the time, particularly for pattern that
  are malloc(X)/free(X)/malloc(X). Now the release will only occur
  after the selected interval, when going through the deallocate path;
- allow release of the `BatchClassId` class: it is releasable, we just
  have to make sure we don't mark the batches containing batches
  pointers as free.
- change the default release interval to 1s for Android to match the
  current Bionic allocator configuration. A patch is coming up to allow
  changing it through `mallopt`.
- lower the smallest class that can be released to `PageSize/64`.

Reviewers: cferris, pcc, eugenis, morehouse, hctim

Subscribers: phosek, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D73507

compiler-rt/lib/scudo/standalone/allocator_config.h

@@ -32,7 +32,7 @@ struct DefaultConfig {
   // 512KB regions
   typedef SizeClassAllocator32<SizeClassMap, 19U> Primary;
 #endif
-  typedef MapAllocator<> Secondary;
+  typedef MapAllocator<MapAllocatorCache<>> Secondary;
   template <class A> using TSDRegistryT = TSDRegistryExT<A>; // Exclusive
 };
 
@@ -47,7 +47,7 @@ struct AndroidConfig {
   // 512KB regions
   typedef SizeClassAllocator32<SizeClassMap, 19U> Primary;
 #endif
-  typedef MapAllocator<> Secondary;
+  typedef MapAllocator<MapAllocatorCache<>> Secondary;
   template <class A>
   using TSDRegistryT = TSDRegistrySharedT<A, 2U>; // Shared, max 2 TSDs.
 };
@@ -61,7 +61,7 @@ struct AndroidSvelteConfig {
   // 64KB regions
   typedef SizeClassAllocator32<SizeClassMap, 16U> Primary;
 #endif
-  typedef MapAllocator<0U> Secondary;
+  typedef MapAllocator<MapAllocatorCache<4U, 1UL << 18>> Secondary;
   template <class A>
   using TSDRegistryT = TSDRegistrySharedT<A, 1U>; // Shared, only 1 TSD.
 };
@@ -70,7 +70,7 @@ struct AndroidSvelteConfig {
 struct FuchsiaConfig {
   // 1GB Regions
   typedef SizeClassAllocator64<DefaultSizeClassMap, 30U> Primary;
-  typedef MapAllocator<0U> Secondary;
+  typedef MapAllocator<MapAllocatorNoCache> Secondary;
   template <class A>
   using TSDRegistryT = TSDRegistrySharedT<A, 8U>; // Shared, max 8 TSDs.
 };

compiler-rt/lib/scudo/standalone/combined.h

@@ -141,8 +141,9 @@ public:
         static_cast<u32>(getFlags()->quarantine_max_chunk_size);
 
     Stats.initLinkerInitialized();
-    Primary.initLinkerInitialized(getFlags()->release_to_os_interval_ms);
-    Secondary.initLinkerInitialized(&Stats);
+    const s32 ReleaseToOsIntervalMs = getFlags()->release_to_os_interval_ms;
+    Primary.initLinkerInitialized(ReleaseToOsIntervalMs);
+    Secondary.initLinkerInitialized(&Stats, ReleaseToOsIntervalMs);
 
     Quarantine.init(
         static_cast<uptr>(getFlags()->quarantine_size_kb << 10),

compiler-rt/lib/scudo/standalone/flags.inc

@@ -45,6 +45,6 @@ SCUDO_FLAG(bool, may_return_null, true,
            "returning NULL in otherwise non-fatal error scenarios, eg: OOM, "
            "invalid allocation alignments, etc.")
 
-SCUDO_FLAG(int, release_to_os_interval_ms, 5000,
+SCUDO_FLAG(int, release_to_os_interval_ms, SCUDO_ANDROID ? 1000 : 5000,
            "Interval (in milliseconds) at which to attempt release of unused "
            "memory to the OS. Negative values disable the feature.")

compiler-rt/lib/scudo/standalone/primary32.h

@@ -74,8 +74,7 @@ public:
       Sci->RandState = getRandomU32(&Seed);
       // See comment in the 64-bit primary about releasing smaller size classes.
       Sci->CanRelease = (ReleaseToOsInterval >= 0) &&
-                        (I != SizeClassMap::BatchClassId) &&
-                        (getSizeByClassId(I) >= (PageSize / 32));
+                        (getSizeByClassId(I) >= (PageSize / 64));
     }
     ReleaseToOsIntervalMs = ReleaseToOsInterval;
   }
@@ -385,7 +384,7 @@ private:
       if (IntervalMs < 0)
         return 0;
       if (Sci->ReleaseInfo.LastReleaseAtNs +
-              static_cast<uptr>(IntervalMs) * 1000000ULL >
+              static_cast<u64>(IntervalMs) * 1000000 >
           getMonotonicTime()) {
         return 0; // Memory was returned recently.
       }

compiler-rt/lib/scudo/standalone/primary64.h

@@ -87,8 +87,7 @@ public:
       // limit is mostly arbitrary and based on empirical observations.
       // TODO(kostyak): make the lower limit a runtime option
       Region->CanRelease = (ReleaseToOsInterval >= 0) &&
-                           (I != SizeClassMap::BatchClassId) &&
-                           (getSizeByClassId(I) >= (PageSize / 32));
+                           (getSizeByClassId(I) >= (PageSize / 64));
       Region->RandState = getRandomU32(&Seed);
     }
     ReleaseToOsIntervalMs = ReleaseToOsInterval;
@@ -401,7 +400,7 @@ private:
       if (IntervalMs < 0)
         return 0;
       if (Region->ReleaseInfo.LastReleaseAtNs +
-              static_cast<uptr>(IntervalMs) * 1000000ULL >
+              static_cast<u64>(IntervalMs) * 1000000 >
           getMonotonicTime()) {
         return 0; // Memory was returned recently.
       }

compiler-rt/lib/scudo/standalone/release.h

@@ -200,7 +200,13 @@ releaseFreeMemoryToOS(const IntrusiveList<TransferBatchT> &FreeList, uptr Base,
   if (BlockSize <= PageSize && PageSize % BlockSize == 0) {
     // Each chunk affects one page only.
     for (const auto &It : FreeList) {
-      for (u32 I = 0; I < It.getCount(); I++) {
+      // If dealing with a TransferBatch, the first pointer of the batch will
+      // point to the batch itself, we do not want to mark this for release as
+      // the batch is in use, so skip the first entry.
+      const bool IsTransferBatch =
+          (It.getCount() != 0) &&
+          (reinterpret_cast<uptr>(It.get(0)) == reinterpret_cast<uptr>(&It));
+      for (u32 I = IsTransferBatch ? 1 : 0; I < It.getCount(); I++) {
         const uptr P = reinterpret_cast<uptr>(It.get(I));
         if (P >= Base && P < End)
           Counters.inc((P - Base) >> PageSizeLog);
@@ -209,7 +215,11 @@ releaseFreeMemoryToOS(const IntrusiveList<TransferBatchT> &FreeList, uptr Base,
   } else {
     // In all other cases chunks might affect more than one page.
     for (const auto &It : FreeList) {
-      for (u32 I = 0; I < It.getCount(); I++) {
+      // See TransferBatch comment above.
+      const bool IsTransferBatch =
+          (It.getCount() != 0) &&
+          (reinterpret_cast<uptr>(It.get(0)) == reinterpret_cast<uptr>(&It));
+      for (u32 I = IsTransferBatch ? 1 : 0; I < It.getCount(); I++) {
         const uptr P = reinterpret_cast<uptr>(It.get(I));
         if (P >= Base && P < End)
           Counters.incRange((P - Base) >> PageSizeLog,

compiler-rt/lib/scudo/standalone/secondary.h

@@ -48,20 +48,183 @@ static Header *getHeader(const void *Ptr) {
 
 } // namespace LargeBlock
 
-template <uptr MaxFreeListSize = 32U> class MapAllocator {
+class MapAllocatorNoCache {
 public:
-  // Ensure the freelist is disabled on Fuchsia, since it doesn't support
-  // releasing Secondary blocks yet.
-  static_assert(!SCUDO_FUCHSIA || MaxFreeListSize == 0U, "");
+  void initLinkerInitialized(UNUSED s32 ReleaseToOsInterval) {}
+  void init(UNUSED s32 ReleaseToOsInterval) {}
+  bool retrieve(UNUSED uptr Size, UNUSED LargeBlock::Header **H) {
+    return false;
+  }
+  bool store(UNUSED LargeBlock::Header *H) { return false; }
+  static bool canCache(UNUSED uptr Size) { return false; }
+  void disable() {}
+  void enable() {}
+};
 
-  void initLinkerInitialized(GlobalStats *S) {
+template <uptr MaxEntriesCount = 32U, uptr MaxEntrySize = 1UL << 19>
+class MapAllocatorCache {
+public:
+  // Fuchsia doesn't allow releasing Secondary blocks yet. Note that 0 length
+  // arrays are an extension for some compilers.
+  // FIXME(kostyak): support (partially) the cache on Fuchsia.
+  static_assert(!SCUDO_FUCHSIA || MaxEntriesCount == 0U, "");
+
+  void initLinkerInitialized(s32 ReleaseToOsInterval) {
+    ReleaseToOsIntervalMs = ReleaseToOsInterval;
+  }
+  void init(s32 ReleaseToOsInterval) {
+    memset(this, 0, sizeof(*this));
+    initLinkerInitialized(ReleaseToOsInterval);
+  }
+
+  bool store(LargeBlock::Header *H) {
+    bool EntryCached = false;
+    bool EmptyCache = false;
+    const u64 Time = getMonotonicTime();
+    {
+      ScopedLock L(Mutex);
+      if (EntriesCount == MaxEntriesCount) {
+        if (IsFullEvents++ == 4U)
+          EmptyCache = true;
+      } else {
+        for (uptr I = 0; I < MaxEntriesCount; I++) {
+          if (Entries[I].Block)
+            continue;
+          if (I != 0)
+            Entries[I] = Entries[0];
+          Entries[0].Block = reinterpret_cast<uptr>(H);
+          Entries[0].BlockEnd = H->BlockEnd;
+          Entries[0].MapBase = H->MapBase;
+          Entries[0].MapSize = H->MapSize;
+          Entries[0].Time = Time;
+          EntriesCount++;
+          EntryCached = true;
+          break;
+        }
+      }
+    }
+    if (EmptyCache)
+      empty();
+    else if (ReleaseToOsIntervalMs >= 0)
+      releaseOlderThan(Time -
+                       static_cast<u64>(ReleaseToOsIntervalMs) * 1000000);
+    return EntryCached;
+  }
+
+  bool retrieve(uptr Size, LargeBlock::Header **H) {
+    ScopedLock L(Mutex);
+    if (EntriesCount == 0)
+      return false;
+    for (uptr I = 0; I < MaxEntriesCount; I++) {
+      if (!Entries[I].Block)
+        continue;
+      const uptr BlockSize = Entries[I].BlockEnd - Entries[I].Block;
+      if (Size > BlockSize)
+        continue;
+      if (Size < BlockSize - getPageSizeCached() * 4U)
+        continue;
+      *H = reinterpret_cast<LargeBlock::Header *>(Entries[I].Block);
+      Entries[I].Block = 0;
+      (*H)->BlockEnd = Entries[I].BlockEnd;
+      (*H)->MapBase = Entries[I].MapBase;
+      (*H)->MapSize = Entries[I].MapSize;
+      EntriesCount--;
+      return true;
+    }
+    return false;
+  }
+
+  static bool canCache(uptr Size) {
+    return MaxEntriesCount != 0U && Size <= MaxEntrySize;
+  }
+
+  void disable() { Mutex.lock(); }
+
+  void enable() { Mutex.unlock(); }
+
+private:
+  void empty() {
+    struct {
+      void *MapBase;
+      uptr MapSize;
+      MapPlatformData Data;
+    } MapInfo[MaxEntriesCount];
+    uptr N = 0;
+    {
+      ScopedLock L(Mutex);
+      for (uptr I = 0; I < MaxEntriesCount; I++) {
+        if (!Entries[I].Block)
+          continue;
+        MapInfo[N].MapBase = reinterpret_cast<void *>(Entries[I].MapBase);
+        MapInfo[N].MapSize = Entries[I].MapSize;
+        MapInfo[N].Data = Entries[I].Data;
+        Entries[I].Block = 0;
+        N++;
+      }
+      EntriesCount = 0;
+      IsFullEvents = 0;
+    }
+    for (uptr I = 0; I < N; I++)
+      unmap(MapInfo[I].MapBase, MapInfo[I].MapSize, UNMAP_ALL,
+            &MapInfo[I].Data);
+  }
+
+  void releaseOlderThan(u64 Time) {
+    struct {
+      uptr Block;
+      uptr BlockSize;
+      MapPlatformData Data;
+    } BlockInfo[MaxEntriesCount];
+    uptr N = 0;
+    {
+      ScopedLock L(Mutex);
+      if (!EntriesCount)
+        return;
+      for (uptr I = 0; I < MaxEntriesCount; I++) {
+        if (!Entries[I].Block || !Entries[I].Time)
+          continue;
+        if (Entries[I].Time > Time)
+          continue;
+        BlockInfo[N].Block = Entries[I].Block;
+        BlockInfo[N].BlockSize = Entries[I].BlockEnd - Entries[I].Block;
+        BlockInfo[N].Data = Entries[I].Data;
+        Entries[I].Time = 0;
+        N++;
+      }
+    }
+    for (uptr I = 0; I < N; I++)
+      releasePagesToOS(BlockInfo[I].Block, 0, BlockInfo[I].BlockSize,
+                       &BlockInfo[I].Data);
+  }
+
+  struct CachedBlock {
+    uptr Block;
+    uptr BlockEnd;
+    uptr MapBase;
+    uptr MapSize;
+    MapPlatformData Data;
+    u64 Time;
+  };
+
+  HybridMutex Mutex;
+  CachedBlock Entries[MaxEntriesCount];
+  u32 EntriesCount;
+  uptr LargestSize;
+  u32 IsFullEvents;
+  s32 ReleaseToOsIntervalMs;
+};
+
+template <class CacheT> class MapAllocator {
+public:
+  void initLinkerInitialized(GlobalStats *S, s32 ReleaseToOsInterval = -1) {
+    Cache.initLinkerInitialized(ReleaseToOsInterval);
     Stats.initLinkerInitialized();
     if (LIKELY(S))
       S->link(&Stats);
   }
-  void init(GlobalStats *S) {
+  void init(GlobalStats *S, s32 ReleaseToOsInterval = -1) {
     memset(this, 0, sizeof(*this));
-    initLinkerInitialized(S);
+    initLinkerInitialized(S, ReleaseToOsInterval);
   }
 
   void *allocate(uptr Size, uptr AlignmentHint = 0, uptr *BlockEnd = nullptr,
@@ -79,22 +242,28 @@ public:
 
   void getStats(ScopedString *Str) const;
 
-  void disable() { Mutex.lock(); }
+  void disable() {
+    Mutex.lock();
+    Cache.disable();
+  }
 
-  void enable() { Mutex.unlock(); }
+  void enable() {
+    Cache.enable();
+    Mutex.unlock();
+  }
 
   template <typename F> void iterateOverBlocks(F Callback) const {
     for (const auto &H : InUseBlocks)
       Callback(reinterpret_cast<uptr>(&H) + LargeBlock::getHeaderSize());
   }
 
-  static uptr getMaxFreeListSize(void) { return MaxFreeListSize; }
+  static uptr canCache(uptr Size) { return CacheT::canCache(Size); }
 
 private:
+  CacheT Cache;
+
   HybridMutex Mutex;
   DoublyLinkedList<LargeBlock::Header> InUseBlocks;
-  // The free list is sorted based on the committed size of blocks.
-  DoublyLinkedList<LargeBlock::Header> FreeBlocks;
   uptr AllocatedBytes;
   uptr FreedBytes;
   uptr LargestSize;
@@ -114,35 +283,32 @@ private:
 // For allocations requested with an alignment greater than or equal to a page,
 // the committed memory will amount to something close to Size - AlignmentHint
 // (pending rounding and headers).
-template <uptr MaxFreeListSize>
-void *MapAllocator<MaxFreeListSize>::allocate(uptr Size, uptr AlignmentHint,
-                                              uptr *BlockEnd,
-                                              bool ZeroContents) {
+template <class CacheT>
+void *MapAllocator<CacheT>::allocate(uptr Size, uptr AlignmentHint,
+                                     uptr *BlockEnd, bool ZeroContents) {
   DCHECK_GE(Size, AlignmentHint);
   const uptr PageSize = getPageSizeCached();
   const uptr RoundedSize =
       roundUpTo(Size + LargeBlock::getHeaderSize(), PageSize);
 
-  if (MaxFreeListSize && AlignmentHint < PageSize) {
-    ScopedLock L(Mutex);
-    for (auto &H : FreeBlocks) {
-      const uptr FreeBlockSize = H.BlockEnd - reinterpret_cast<uptr>(&H);
-      if (FreeBlockSize < RoundedSize)
-        continue;
-      // Candidate free block should only be at most 4 pages larger.
-      if (FreeBlockSize > RoundedSize + 4 * PageSize)
-        break;
-      FreeBlocks.remove(&H);
-      InUseBlocks.push_back(&H);
-      AllocatedBytes += FreeBlockSize;
-      NumberOfAllocs++;
-      Stats.add(StatAllocated, FreeBlockSize);
+  if (AlignmentHint < PageSize && CacheT::canCache(RoundedSize)) {
+    LargeBlock::Header *H;
+    if (Cache.retrieve(RoundedSize, &H)) {
       if (BlockEnd)
-        *BlockEnd = H.BlockEnd;
-      void *Ptr = reinterpret_cast<void *>(reinterpret_cast<uptr>(&H) +
+        *BlockEnd = H->BlockEnd;
+      void *Ptr = reinterpret_cast<void *>(reinterpret_cast<uptr>(H) +
                                            LargeBlock::getHeaderSize());
       if (ZeroContents)
-        memset(Ptr, 0, H.BlockEnd - reinterpret_cast<uptr>(Ptr));
+        memset(Ptr, 0, H->BlockEnd - reinterpret_cast<uptr>(Ptr));
+      const uptr BlockSize = H->BlockEnd - reinterpret_cast<uptr>(H);
+      {
+        ScopedLock L(Mutex);
+        InUseBlocks.push_back(H);
+        AllocatedBytes += BlockSize;
+        NumberOfAllocs++;
+        Stats.add(StatAllocated, BlockSize);
+        Stats.add(StatMapped, H->MapSize);
+      }
       return Ptr;
     }
   }
@@ -191,6 +357,8 @@ void *MapAllocator<MaxFreeListSize>::allocate(uptr Size, uptr AlignmentHint,
   H->MapSize = MapEnd - MapBase;
   H->BlockEnd = CommitBase + CommitSize;
   H->Data = Data;
+  if (BlockEnd)
+    *BlockEnd = CommitBase + CommitSize;
   {
     ScopedLock L(Mutex);
     InUseBlocks.push_back(H);
@@ -201,52 +369,31 @@ void *MapAllocator<MaxFreeListSize>::allocate(uptr Size, uptr AlignmentHint,
     Stats.add(StatAllocated, CommitSize);
     Stats.add(StatMapped, H->MapSize);
   }
-  if (BlockEnd)
-    *BlockEnd = CommitBase + CommitSize;
   return reinterpret_cast<void *>(Ptr + LargeBlock::getHeaderSize());
 }
 
-template <uptr MaxFreeListSize>
-void MapAllocator<MaxFreeListSize>::deallocate(void *Ptr) {
+template <class CacheT> void MapAllocator<CacheT>::deallocate(void *Ptr) {
   LargeBlock::Header *H = LargeBlock::getHeader(Ptr);
   const uptr Block = reinterpret_cast<uptr>(H);
+  const uptr CommitSize = H->BlockEnd - Block;
   {
     ScopedLock L(Mutex);
     InUseBlocks.remove(H);
-    const uptr CommitSize = H->BlockEnd - Block;
     FreedBytes += CommitSize;
     NumberOfFrees++;
     Stats.sub(StatAllocated, CommitSize);
-    if (MaxFreeListSize && FreeBlocks.size() < MaxFreeListSize) {
-      bool Inserted = false;
-      for (auto &F : FreeBlocks) {
-        const uptr FreeBlockSize = F.BlockEnd - reinterpret_cast<uptr>(&F);
-        if (FreeBlockSize >= CommitSize) {
-          FreeBlocks.insert(H, &F);
-          Inserted = true;
-          break;
-        }
-      }
-      if (!Inserted)
-        FreeBlocks.push_back(H);
-      const uptr RoundedAllocationStart =
-          roundUpTo(Block + LargeBlock::getHeaderSize(), getPageSizeCached());
-      MapPlatformData Data = H->Data;
-      // TODO(kostyak): use release_to_os_interval_ms
-      releasePagesToOS(Block, RoundedAllocationStart - Block,
-                       H->BlockEnd - RoundedAllocationStart, &Data);
-      return;
-    }
     Stats.sub(StatMapped, H->MapSize);
   }
+  if (CacheT::canCache(CommitSize) && Cache.store(H))
+    return;
   void *Addr = reinterpret_cast<void *>(H->MapBase);
   const uptr Size = H->MapSize;
   MapPlatformData Data = H->Data;
   unmap(Addr, Size, UNMAP_ALL, &Data);
 }
 
-template <uptr MaxFreeListSize>
-void MapAllocator<MaxFreeListSize>::getStats(ScopedString *Str) const {
+template <class CacheT>
+void MapAllocator<CacheT>::getStats(ScopedString *Str) const {
   Str->append(
       "Stats: MapAllocator: allocated %zu times (%zuK), freed %zu times "
       "(%zuK), remains %zu (%zuK) max %zuM\n",

compiler-rt/lib/scudo/standalone/tests/combined_test.cpp

@@ -347,7 +347,7 @@ struct DeathConfig {
   // Tiny allocator, its Primary only serves chunks of 1024 bytes.
   using DeathSizeClassMap = scudo::SizeClassMap<1U, 10U, 10U, 10U, 1U, 10U>;
   typedef scudo::SizeClassAllocator64<DeathSizeClassMap, 20U> Primary;
-  typedef scudo::MapAllocator<0U> Secondary;
+  typedef scudo::MapAllocator<scudo::MapAllocatorNoCache> Secondary;
   template <class A> using TSDRegistryT = scudo::TSDRegistrySharedT<A, 1U>;
 };
 

compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp

@@ -29,8 +29,8 @@ template <class SecondaryT> static void testSecondaryBasic(void) {
   memset(P, 'A', Size);
   EXPECT_GE(SecondaryT::getBlockSize(P), Size);
   L->deallocate(P);
-  // If we are not using a free list, blocks are unmapped on deallocation.
-  if (SecondaryT::getMaxFreeListSize() == 0U)
+  // If the Secondary can't cache that pointer, it will be unmapped.
+  if (!SecondaryT::canCache(Size))
     EXPECT_DEATH(memset(P, 'A', Size), "");
 
   const scudo::uptr Align = 1U << 16;
@@ -55,17 +55,18 @@ template <class SecondaryT> static void testSecondaryBasic(void) {
 }
 
 TEST(ScudoSecondaryTest, SecondaryBasic) {
-  testSecondaryBasic<scudo::MapAllocator<0U>>();
+  testSecondaryBasic<scudo::MapAllocator<scudo::MapAllocatorNoCache>>();
 #if !SCUDO_FUCHSIA
-  testSecondaryBasic<scudo::MapAllocator<>>();
-  testSecondaryBasic<scudo::MapAllocator<64U>>();
+  testSecondaryBasic<scudo::MapAllocator<scudo::MapAllocatorCache<>>>();
+  testSecondaryBasic<
+      scudo::MapAllocator<scudo::MapAllocatorCache<64U, 1UL << 20>>>();
 #endif
 }
 
 #if SCUDO_FUCHSIA
-using LargeAllocator = scudo::MapAllocator<0U>;
+using LargeAllocator = scudo::MapAllocator<scudo::MapAllocatorNoCache>;
 #else
-using LargeAllocator = scudo::MapAllocator<>;
+using LargeAllocator = scudo::MapAllocator<scudo::MapAllocatorCache<>>;
 #endif
 
 // This exercises a variety of combinations of size and alignment for the