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Lioncash c51f8563a6 ring_buffer: Use std::hardware_destructive_interference_size to determine alignment size for avoiding false sharing MSVC 19.11 (A.K.A. VS 15.3)'s C++ standard library implements P0154R1 (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0154r1.html) which defines two new constants within the <new> header, std::hardware_destructive_interference_size and std::hardware_constructive_interference_size. std::hardware_destructive_interference_size defines the minimum recommended offset between two concurrently-accessed objects to avoid performance degradation due to contention introduced by the implementation (with the lower-bound being at least alignof(max_align_t)). In other words, the minimum offset between objects necessary to avoid false-sharing. std::hardware_constructive_interference_size on the other hand defines the maximum recommended size of contiguous memory occupied by two objects accessed wth temporal locality by concurrent threads (also defined to be at least alignof(max_align_t)). In other words the maximum size to promote true-sharing. So we can simply use this facility to determine the ideal alignment size. Unfortunately, only MSVC supports this right now, so we need to enclose it within an ifdef for the time being.	7 years ago
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UtilityFunctions.ps1	Implement Citra pull 3043	8 years ago

ring_buffer: Use std::hardware_destructive_interference_size to determine alignment size for avoiding false sharing

MSVC 19.11 (A.K.A. VS 15.3)'s C++ standard library implements P0154R1
(http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0154r1.html)
which defines two new constants within the <new> header, std::hardware_destructive_interference_size
and std::hardware_constructive_interference_size.

std::hardware_destructive_interference_size defines the minimum
recommended offset between two concurrently-accessed objects to avoid
performance degradation due to contention introduced by the
implementation (with the lower-bound being at least alignof(max_align_t)).
In other words, the minimum offset between objects necessary to avoid
false-sharing.

std::hardware_constructive_interference_size on the other hand defines
the maximum recommended size of contiguous memory occupied by two
objects accessed wth temporal locality by concurrent threads (also
defined to be at least alignof(max_align_t)). In other words the maximum
size to promote true-sharing.

So we can simply use this facility to determine the ideal alignment
size. Unfortunately, only MSVC supports this right now, so we need to
enclose it within an ifdef for the time being.

7 years ago

UtilityFunctions.ps1

Implement Citra pull 3043

8 years ago