There is an optimization opportunity for the widespread use-case when a
resource is read from classpath using
`getClass().getClassLoader().getResource()` or
`getClass().getClassLoader().getResourceAsStream()`.
Pay attention to lines starting from 261. In case I run something like
var props = getClass().getClassLoader().getResource("/application.properties");
I get into the if-else block starting from 251 and here 'separator' variable is
an empty String. In this case we can skip 'separator' from concatenation chain
and use `String.concat()` as there are only two items concatenated.
In the opposite case `separator` variable is `"/"` and at the same time `ind`
variable is `-1`. This means that expression `path.substring(0, ind + 1)`
always returns an empty String and again can be excluded from concatenation
chain allowing usage of `String.concat()` which allows to dodge utilization of
`StringBuilder` (here `StringConcatFactory` is not available, see
https://github.com/openjdk/jdk/pull/3627)
In the next else-block, starting from 274, again, `String.concat()` is
applicable.
In another if-else block, starting from 277, when id is 0 again
path.substring(0, ind) returns empty String making concatenation pointless and
avoidable.
There are also some other minor clean-ups possible regarding constant
conditions (lines 252 and 161).
The change allows to reduce significantly resource look-up costs for a very
wide-spread case:
@State(Scope.Benchmark)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Fork(jvmArgsAppend = {"-Xms2g", "-Xmx2g"})
public class ClassGetResourceBenchmark {
private final Class<?> clazz = getClass();
@Benchmark
public URL getResource() {
return clazz.getResource("/application.properties");
}
}
The change allows to reduce memory consumption significantly:
before
Benchmark Mode
Cnt Score Error Units
ClassGetResourceBenchmark.getResource avgt
100 1649,367 ± 5,904 ns/op
ClassGetResourceBenchmark.getResource:·gc.alloc.rate avgt
100 619,204 ± 2,413 MB/sec
ClassGetResourceBenchmark.getResource:·gc.alloc.rate.norm avgt
100 1339,232 ± 4,909 B/op
ClassGetResourceBenchmark.getResource:·gc.churn.G1_Eden_Space avgt
100 627,192 ± 74,972 MB/sec
ClassGetResourceBenchmark.getResource:·gc.churn.G1_Eden_Space.norm avgt
100 1356,681 ± 162,354 B/op
ClassGetResourceBenchmark.getResource:·gc.churn.G1_Survivor_Space avgt
100 0,119 ± 0,100 MB/sec
ClassGetResourceBenchmark.getResource:·gc.churn.G1_Survivor_Space.norm avgt
100 0,257 ± 0,217 B/op
ClassGetResourceBenchmark.getResource:·gc.count avgt
100 128,000 counts
ClassGetResourceBenchmark.getResource:·gc.time avgt
100 227,000 ms
after
Benchmark Mode
Cnt Score Error Units
ClassGetResourceBenchmark.getResource avgt
100 1599,948 ± 4,115 ns/op
ClassGetResourceBenchmark.getResource:·gc.alloc.rate avgt
100 358,434 ± 0,922 MB/sec
ClassGetResourceBenchmark.getResource:·gc.alloc.rate.norm avgt
100 752,016 ± 0,004 B/op
ClassGetResourceBenchmark.getResource:·gc.churn.G1_Eden_Space avgt
100 342,778 ± 76,490 MB/sec
ClassGetResourceBenchmark.getResource:·gc.churn.G1_Eden_Space.norm avgt
100 719,264 ± 160,513 B/op
ClassGetResourceBenchmark.getResource:·gc.churn.G1_Survivor_Space avgt
100 0,008 ± 0,005 MB/sec
ClassGetResourceBenchmark.getResource:·gc.churn.G1_Survivor_Space.norm avgt
100 0,017 ± 0,010 B/op
ClassGetResourceBenchmark.getResource:·gc.count avgt
100 70,000 counts
ClassGetResourceBenchmark.getResource:·gc.time avgt
100 151,000 ms
-------------
Commit messages:
- 8267840: Improve URLStreamHandler.parseURL()
Changes: https://git.openjdk.java.net/jdk/pull/4526/files
Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4526&range=00
Issue: https://bugs.openjdk.java.net/browse/JDK-8267840
Stats: 25 lines in 1 file changed: 3 ins; 8 del; 14 mod
Patch: https://git.openjdk.java.net/jdk/pull/4526.diff
Fetch: git fetch https://git.openjdk.java.net/jdk pull/4526/head:pull/4526
PR: https://git.openjdk.java.net/jdk/pull/4526
