danielsun1106 edited a comment on issue #1135: GROOVY-8298: Slow Performance Caused by Invoke Dynamic URL: https://github.com/apache/groovy/pull/1135#issuecomment-570811643 Jochen, the main idea can be described as the following code: ```java if (cacheHits(receiverCassName)) { // Try to find the cached MethodHandle // the main logic of `fromCache` MethodHandle mh = lruCache.get(receiverCassName); // find the cached MethodHandle again... return mh.invokeExact(...); } else { // fallback, and put the fallback methodhandle to the inline cache(LRU) for reuse // the main logic of `selectMethod` Selector selector = Selector.getSelector(...); selector.setCallSiteTarget(); MethodHandle mh = selector.handle.asSpreader(...).asType(...); lruCache.put(receiverCassName, mh); // cache the methodhandle return mh.invokeExact(...); } ``` As the inline cache is implemented as LRU cache, and `cacheHits` and `fromCache` are executed in two steps(not atomic), so if `cacheHits` returns `true`(means cached methodhandle found), `fromCache` find the same cached methodhandle from LRU cache again, the result probably is `null` as cached methodhandle may be cleared according to the rule of LRU... I use `ThreadLocal` to avoid the above concurrent issue. Also, we have inline cache for callsite, so `setTarget` can be avoided, which causes the poor performance as the GROOVY-8298 shown.
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