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perf: look up case sensitivity without locking - #1584
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rubenporras merged 1 commit intoOct 29, 2026
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ConcurrentHashMap.computeIfAbsent checks only the first node of a bin without locking, so a key that shares a bin with another key locks the bin on every call, even when it is already present. EClasses use identity hash codes, so whether this happens differs from run to run. When it hit a frequently used EClass, the compiler's request workers serialized on that bin while resolving proxies (JDK-8161372). Read the cache with get() first and only call computeIfAbsent on a miss. Also compare case-insensitively first, so that the cache is only consulted for candidate matches rather than for every element of the containment list.
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LGTM. The get() before computeIfAbsent makes hits lock-free, and the reordered condition matches the same objects. Optional: a test for case-sensitive vs. insensitive sibling lookup, and a note that the contention has been there since d023749 (17.2.0).
Posted by Claude Code on behalf of @joaodinissf.
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ConcurrentHashMap.computeIfAbsent checks only the first node of a bin without locking, so a key that shares a bin with another key locks the bin on every call, even when it is already present. EClasses use identity hash codes, so whether this happens differs from run to run. When it hit a frequently used EClass, the compiler's request workers serialized on that bin while resolving proxies (JDK-8161372).
Read the cache with get() first and only call computeIfAbsent on a miss. Also compare case-insensitively first, so that the cache is only consulted for candidate matches rather than for every element of the containment list.