On Fri, 18 Jun 2021 07:31:14 GMT, Сергей Цыпанов
<github.com+10835776+stsypa...@openjdk.org> wrote:
> 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
Hi Sergey,
The logics seems correct - but what test did you run? have you run tier1 and
tier2?
best regards,
-- daniel
-------------
PR: https://git.openjdk.java.net/jdk/pull/4526
