ceph/src/common/allocator.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3
   4 #ifndef CEPH_COMMON_ALLOCATOR_H
   5 #define CEPH_COMMON_ALLOCATOR_H
   6
   7 #include "acconfig.h"
   8
   9 #ifdef LIBTCMALLOC_MISSING_ALIGNED_ALLOC
  10 #include <malloc.h>
  11 #include <new>
  12 #endif
  13 #include <memory>
  14
  15 namespace ceph {
  16
  17 #ifdef LIBTCMALLOC_MISSING_ALIGNED_ALLOC
  18
  19 // If libtcmalloc is missing 'aligned_alloc', provide a new allocator class that
  20 // uses memalign which is what newer versions of tcmalloc do internally. C++17
  21 // will automatically use 'operator new(size_t, align_val_t)' for aligned
  22 // structures, which will invoke the missing 'aligned_alloc' tcmalloc function.
  23 // This method was added to tcmalloc (gperftools) in commit d406f228 after
  24 // the 2.6.1 release was tagged.
  25 template <typename T>
  26 struct allocator : public std::allocator<T> {
  27   using pointer = typename std::allocator<T>::pointer;
  28   using size_type = typename std::allocator<T>::size_type;
  29
  30   template<class U>
  31   struct rebind {
  32     typedef allocator<U> other;
  33   };
  34
  35   allocator() noexcept {
  36   }
  37
  38   allocator(const allocator& other) noexcept : std::allocator<T>(other) {
  39   }
  40
  41   template <class U>
  42   allocator(const allocator<U>& other) noexcept : std::allocator<T>(other) {
  43   }
  44
  45   pointer allocate(size_type n, const void* hint = nullptr) {
  46     if (n > this->max_size()) {
  47       throw std::bad_alloc();
  48     }
  49
  50     if (alignof(T) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
  51       return static_cast<T*>(memalign(alignof(T), n * sizeof(T)));
  52     }
  53     return std::allocator<T>::allocate(n, hint);
  54   }
  55 };
  56
  57 #else  // LIBTCMALLOC_MISSING_ALIGNED_ALLOC
  58
  59 // re-use the full std::allocator implementation if tcmalloc is functional
  60
  61 template <typename T>
  62 using allocator = std::allocator<T>;
  63
  64 #endif // LIBTCMALLOC_MISSING_ALIGNED_ALLOC
  65
  66 } // namespace ceph
  67
  68 #endif // CEPH_COMMON_ALLOCATOR_H
  69