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Merge pull request #1352 from lioncash/sharing

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ring_buffer: Use std::hardware_destructive_interference_size to determine alignment size for avoiding false sharing
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bunnei 2018-09-20 23:29:10 -04:00 committed by GitHub
commit a0db7e2cf9
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1 changed files with 11 additions and 3 deletions
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14
src/common/ring_buffer.h
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@ -9,6 +9,7 @@
#include <atomic> #include <atomic>
#include <cstddef> #include <cstddef>
#include <cstring> #include <cstring>
#include <new>
#include <type_traits> #include <type_traits>
#include <vector> #include <vector>
#include "common/common_types.h" #include "common/common_types.h"
@ -29,7 +30,7 @@ class RingBuffer {
static_assert(capacity < std::numeric_limits<std::size_t>::max() / 2 / granularity); static_assert(capacity < std::numeric_limits<std::size_t>::max() / 2 / granularity);
static_assert((capacity & (capacity - 1)) == 0, "capacity must be a power of two"); static_assert((capacity & (capacity - 1)) == 0, "capacity must be a power of two");
// Ensure lock-free. // Ensure lock-free.
static_assert(std::atomic<std::size_t>::is_always_lock_free); static_assert(std::atomic_size_t::is_always_lock_free);
public: public:
/// Pushes slots into the ring buffer /// Pushes slots into the ring buffer
@ -102,8 +103,15 @@ public:
private: private:
// It is important to align the below variables for performance reasons: // It is important to align the below variables for performance reasons:
// Having them on the same cache-line would result in false-sharing between them. // Having them on the same cache-line would result in false-sharing between them.
alignas(128) std::atomic<std::size_t> m_read_index{0}; // TODO: Remove this ifdef whenever clang and GCC support
alignas(128) std::atomic<std::size_t> m_write_index{0}; // std::hardware_destructive_interference_size.
#if defined(_MSC_VER) && _MSC_VER >= 1911
alignas(std::hardware_destructive_interference_size) std::atomic_size_t m_read_index{0};
alignas(std::hardware_destructive_interference_size) std::atomic_size_t m_write_index{0};
#else
alignas(128) std::atomic_size_t m_read_index{0};
alignas(128) std::atomic_size_t m_write_index{0};
#endif
std::array<T, granularity * capacity> m_data; std::array<T, granularity * capacity> m_data;
}; };