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Prefer std::atomic over MemoryBarrier when available #19
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Can be closed as duplicate of bitcoin-core/leveldb-subtree#2 |
droark
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Oct 6, 2018
…000 to 4096 on 64-bit systems 4874cb8 Increase maximum number of read-only mmap()s used from 1000 to 4096 on 64 bit systems. (Clem Taylor) Pull request description: By default LevelDB will only mmap() up to 1000 ldb files for reading and then fall back to using file desciptors. The typical linux system has a 'vm.max_map_count = 65530', so mapping only 1000 files seems arbitarily small. Increase this value to another arbitrarily small value, 4096. Tree-SHA512: 42d0978f229603aa882ac47a43ec455be0e27c9c3e4d7e36f7e6b49bab6da7c1bd0d3ffbaca22dfda2a5722fa533d1ce7439e9f99fdedb64df0c4442bbb6a93c
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Also submitted upstream as google/leveldb#449.
In port/atomic_pointer.h, the preference is to use MemoryBarrier if available, and only fall back to std::atomic if it isn't available.
I believe it would be preferable to use std::atomic, as it may allow better performance, and integrates without changes into ThreadSanitizer.
This PR changes the preference to std::atomic if available.