ut0cpu_cache.h

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/** @file include/ut0cpu_cache.h
Utilities related to CPU cache. */
 
#ifndef ut0cpu_cache_h
#define ut0cpu_cache_h
 
#include "ut0ut.h"
namespace ut {
 
/** CPU cache line size */
#ifdef __powerpc__
constexpr size_t INNODB_CACHE_LINE_SIZE = 128;
#else
constexpr size_t INNODB_CACHE_LINE_SIZE = 64;
#endif /* __powerpc__ */
 
/** Default kernel page size (not assuming huge pages support). */
constexpr size_t INNODB_KERNEL_PAGE_SIZE_DEFAULT = 4 * 1024;
 
/**
A utility wrapper class, which adds padding at the end of the wrapped structure,
so that the next object after it is guaranteed to be in the next cache line.
This is to avoid false-sharing.
Use this, as opposed to alignas(), to avoid problems with allocators which do
not handle over-aligned types.
 */
template <typename T>
struct Cacheline_padded : public T {
  char pad[INNODB_CACHE_LINE_SIZE];
  // "Inherit" constructors
  using T::T;
};
 
/**
A utility wrapper class, which aligns T to cacheline boundary.
This is to avoid false-sharing.
*/
template <typename T>
struct alignas(INNODB_CACHE_LINE_SIZE) Cacheline_aligned : public T {
  // "Inherit" constructors
  using T::T;
};
 
} /* namespace ut */
 
#endif /* ut0cpu_cache_h */