large_page_alloc-osx.h

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/** @file include/detail/ut/large_page_alloc-osx.h
 OSX-specific implementation bits and pieces for large (huge) page
 allocations. */
 
#ifndef detail_ut_large_page_alloc_osx_h
#define detail_ut_large_page_alloc_osx_h
 
#include <mach/vm_statistics.h>
#include <sys/mman.h>
#include <sys/types.h>
 
#include "mysqld_error.h"
#include "storage/innobase/include/detail/ut/helper.h"
#include "storage/innobase/include/ut0log.h"
 
extern const size_t large_page_default_size;
 
namespace ut {
namespace detail {
 
/** Superpage size to be used (2MB). */
static constexpr auto SUPER_PAGE_SIZE = VM_FLAGS_SUPERPAGE_SIZE_2MB;
 
/** Allocates memory backed by large (huge) pages.
 
    @param[in] n_bytes Size of storage (in bytes) requested to be allocated.
    @return Pointer to the allocated storage. nullptr if allocation failed.
*/
inline void *large_page_aligned_alloc(size_t n_bytes) {
  // mmap on OSX requires for n_bytes to be a multiple of large-page size
  size_t n_bytes_rounded = pow2_round(n_bytes + (large_page_default_size - 1),
                                      large_page_default_size);
  void *ptr = mmap(nullptr, n_bytes_rounded, PROT_READ | PROT_WRITE,
                   MAP_PRIVATE | MAP_ANON, SUPER_PAGE_SIZE, 0);
  if (unlikely(ptr == (void *)-1)) {
    ib::log_warn(ER_IB_MSG_856)
        << "large_page_aligned_alloc mmap(" << n_bytes_rounded
        << " bytes) failed;"
           " errno "
        << errno;
  }
  return (ptr != (void *)-1) ? ptr : nullptr;
}
 
/** Releases memory backed by large (huge) pages.
 
    @param[in] ptr Pointer to large (huge) page aligned storage.
    @param[in] n_bytes Size of the storage.
    @return Returns true if releasing the large (huge) page succeeded.
 */
inline bool large_page_aligned_free(void *ptr, size_t n_bytes) {
  if (unlikely(!ptr)) return false;
  // Freeing huge-pages require size to be the multiple of huge-page size
  size_t n_bytes_rounded = pow2_round(n_bytes + (large_page_default_size - 1),
                                      large_page_default_size);
  auto ret = munmap(ptr, n_bytes_rounded);
  if (unlikely(ret != 0)) {
    ib::log_error(ER_IB_MSG_858)
        << "large_page_aligned_free munmap(" << ptr << ", " << n_bytes_rounded
        << ") failed;"
           " errno "
        << errno;
  }
  return ret == 0;
}
 
/** Queries the current size of large (huge) pages on running system.
 
    @return Large (huge) page size in bytes.
*/
inline size_t large_page_size() {
  // Return value of this function is hard-coded because of the way how
  // large_page_aligned_alloc is allocating superpages
  // (VM_FLAGS_SUPERPAGE_SIZE_2MB).
  //
  // Nonetheless we can make a compile-time check to detect situations when and
  // if that value may change, in which case we can at least provide a
  // guideline through static_assert message.
  static_assert(
      SUPER_PAGE_SIZE == VM_FLAGS_SUPERPAGE_SIZE_2MB,
      "superpage size is not the one that has been expected (2MB). In case this \
      is a wanted change, please tweak this static_assert _and_ modify this function \
      to return appropriate new superpage size value.");
  return 2 * 1024 * 1024;
}
 
}  // namespace detail
}  // namespace ut
 
#endif