Uses 128 bytes padding to prevent false-sharing #191
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franz1981
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dmlloyd
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Sep 24, 2024
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According to Intel Optimisation Manual, using 128 bytes is safer due to the spatial prefetcher - which can bring 2 cache-lines into L2.
see
Intel Netburst is pretty old but I've observed something similar with AMD Ryzen with multi-NUMA nodes.
See https://morestina.net/blog/1976/a-close-encounter-with-false-sharing as well
I've been hit by the same in Hyperfoil too, see https://github.com/Hyperfoil/Hyperfoil/pull/374/files#diff-03478637fd75a5eb1aef7f5db3b19db102359afba797e0328580dcc83796b735R40
OpenJDK itself seems to prefer 128 bytes: https://github.com/openjdk/jdk/blob/44024826e52373d1613ec366e3f5a9d5bbaefa41/src/hotspot/share/runtime/globals.hpp#L811
and fallback to the cache line only if the cache line exceed the configured default one, see https://github.com/openjdk/jdk/blob/44024826e52373d1613ec366e3f5a9d5bbaefa41/src/hotspot/cpu/x86/vm_version_x86.cpp#L1940-L1942