> 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: Shorter, more to the point code comment block ------------- Changes: - all: https://git.openjdk.org/jdk/pull/30151/files - new: https://git.openjdk.org/jdk/pull/30151/files/6bf512a0..f7fc4254 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=30151&range=07 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=30151&range=06-07 Stats: 6 lines in 1 file changed: 0 ins; 4 del; 2 mod Patch: https://git.openjdk.org/jdk/pull/30151.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/30151/head:pull/30151 PR: https://git.openjdk.org/jdk/pull/30151
