On Thu, 12 Mar 2026 14:07:46 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.
>> * 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:
>
> Unify 'path' variables
The new code is now reasonably concise and easy to reason with. It's a great
improvement compared to the changes proposed in this PR first commit.
test/jdk/java/net/URL/Constructor.java line 267:
> 265: new Entry(null, "file:/path#?", "file:/path#?"),
> 266: new Entry("file:/path", "path?#", "file:/path?#"),
> 267: new Entry(null, "file:", "file:"),
Should we add some entries of the form `<protocol>:///...` ? This also results
in an empty/null authority component.
-------------
PR Review: https://git.openjdk.org/jdk/pull/30151#pullrequestreview-3936983772
PR Review Comment: https://git.openjdk.org/jdk/pull/30151#discussion_r2924963211
