cache-align the shards to improve throughput#303
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Thanks a lot!, will merge. |
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Using CachePadded to cache-align the rwlock shards for improved locking performance. This offers considerable (30-50%) improvements in both latency and throughput perf on my M2.
Note
This increases memory usage. On x86_64, the cache alignment is set to 128. The current size of
RwLock<HashMap<K, V, std::RandomState>>is8 + 16 + 32 = 56bytes. The current size ofRwLock<HashMap<K, V, ahash::RandomState>>is8 + 32 + 32 = 72bytes. So this will double the size of the empty collection. Eg on a 64 core CPU the empty std dashmap size will increase from 14KiB to 32KiB. This size increase is constant though and does not scale per element inserted into the map.Important
This is a breaking change for the raw shards api.
Benchmark results
In this benchmark,
DashMapis the released version 5.3.3DashMap2is this version