On Thu, 12 Mar 2026 14:33:48 GMT, Eirik Bjørsnøs <[email protected]> wrote:
>> This PR optimizes string concatenation in `URL::toExternalForm`. This method >> is called by `URL:toString` and executes often enough to be noticed during >> startup / classloading profiling. It was previously optimized in JDK 10 via >> JDK-8193034, but we can do more. >> >> Key observations: >> >> * The current method concatenates concatenated strings. We can get away with >> less by flattening and concatenating once per call. >> * JIT StringBuilder concat optimizations prefer consecutive append calls >> withot interleaving code / conditionals >> * The current method does not take advantage of the fact that most URL >> components are optional and several are commonly not present. We can >> specialize for those cheaper common concatenations. >> >> This PR reduces runtime with 60% or more, depending on present URL >> components. (Benchmark results in first comment). I also ran the benchmark >> with compilation excluded and found no regressions for the interpreter case. >> >> Working on this PR revealed that current tests miss coverage for the case >> where a query or ref component is the empty string. Some new test cases are >> added to `Constructor.java`. Otherwise, `URL::toString` seems well tested by >> current tests. >> >> Performance refactoring, `noreg-perf`. > > Eirik Bjørsnøs has updated the pull request incrementally with one additional > commit since the last revision: > > Add cases for URLs with empty host components in the form 'protocol:///path' src/java.base/share/classes/java/net/URLStreamHandler.java line 490: > 488: > 489: // Optionality, subtly different for authority > 490: var emptyAuth = u.getAuthority() == null || > u.getAuthority().isEmpty(); Style-wise I think better to use boolean rathe rather var here as you have to look closely to see that the RHS yields a boolean result (it's not obvious from the name "emptyAuth"). ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/30151#discussion_r2925216626
