refactor: move cob thread tracking to a slot pool for performance #10
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bruno-dasilva wants to merge 3 commits into
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refactor: move cob thread tracking to a slot pool for performance #10bruno-dasilva wants to merge 3 commits into
bruno-dasilva wants to merge 3 commits into
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Change Moves cob engine's internal storage/tracking of threads to a slot pool backed by a std::deque instead of a spring::unordered_map, to eek out some extra performance. There's a hack due to ordering requirements of the existing code but I figure a second PR can clean that up - let's keep this PR focused. Context Some instrumentation of our hash maps found that cob was one of the worst users of our spring::unordered_map, because of how many tombstones it would leave behind in the map (cob has constant thread churn). `spring::unordered_map<int, CCobThread> threadInstances` performance over 5000 late game sim frames was: ``` [HashContainerStats] Top 20 containers by total time (ns/op): type | total-ms | find-hit | find-miss | insert | erase | rehash synced map<int, CCobThread> | 3031.91ms | 130ns | 1360ns | 1292ns | 0ns | 219100ns ``` Changing it to a chained hashmap fixed the find-miss() ns per op (since it didnt have to search the entire array of tombstones) but made the find() worse because it had to chase bucket pointers. So, taking a step back and realizing that nothing really iterates on this and the amount of churn it sees, an object pool is probably a better data structure. So let's try it!
bar-benchmark — PR #10candidate sim trimmed mean (ms) with 95% CI on the relative delta
Per-VM distribution box plots (5) |
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