On Wed, 13 Jan 2021 13:48:40 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> Instead of allocating a copy of underlying array via
>> `CharArrayWriter.toCharArray()` and passing it to constructor of String
>> String str = new String(charArrayWriter.toCharArray());
>> we could call `toString()` method
>> String str = charArrayWriter.toString();
>> decoding existing char[] without making a copy. This slightly speeds up the
>> method reducing at the same time memory consumption for decoding URLs with
>> non-latin symbols:
>> @State(Scope.Thread)
>> @BenchmarkMode(Mode.AverageTime)
>> @OutputTimeUnit(TimeUnit.NANOSECONDS)
>> @Fork(jvmArgsAppend = {"-Xms2g", "-Xmx2g"})
>> public class UrlEncoderBenchmark {
>> private static final Charset charset = Charset.defaultCharset();
>> private static final String utf8Url =
>> "https://ru.wikipedia.org/wiki/Организация_Объединённых_Наций";; // UN
>>
>> @Benchmark
>> public String encodeUtf8() {
>> return URLEncoder.encode(utf8Url, charset);
>> }
>> }
>> The benchmark on my maching give the following output:
>> before
>> Benchmark Mode Cnt
>> Score Error Units
>> UrlEncoderBenchmark.encodeUtf8 avgt 100
>> 1166.378 ± 8.411 ns/op
>> UrlEncoderBenchmark.encodeUtf8:·gc.alloc.rate avgt 100
>> 932.944 ± 6.393 MB/sec
>> UrlEncoderBenchmark.encodeUtf8:·gc.alloc.rate.norm avgt 100
>> 1712.193 ± 0.005 B/op
>> UrlEncoderBenchmark.encodeUtf8:·gc.churn.G1_Eden_Space avgt 100
>> 929.221 ± 24.268 MB/sec
>> UrlEncoderBenchmark.encodeUtf8:·gc.churn.G1_Eden_Space.norm avgt 100
>> 1705.444 ± 43.235 B/op
>> UrlEncoderBenchmark.encodeUtf8:·gc.churn.G1_Survivor_Space avgt 100
>> 0.006 ± 0.001 MB/sec
>> UrlEncoderBenchmark.encodeUtf8:·gc.churn.G1_Survivor_Space.norm avgt 100
>> 0.011 ± 0.002 B/op
>> UrlEncoderBenchmark.encodeUtf8:·gc.count avgt 100
>> 652.000 counts
>> UrlEncoderBenchmark.encodeUtf8:·gc.time avgt 100
>> 334.000 ms
>>
>> after
>> Benchmark Mode Cnt
>> Score Error Units
>> UrlEncoderBenchmark.encodeUtf8 avgt 100
>> 1058.851 ± 6.006 ns/op
>> UrlEncoderBenchmark.encodeUtf8:·gc.alloc.rate avgt 100
>> 931.489 ± 5.182 MB/sec
>> UrlEncoderBenchmark.encodeUtf8:·gc.alloc.rate.norm avgt 100
>> 1552.176 ± 0.005 B/op
>> UrlEncoderBenchmark.encodeUtf8:·gc.churn.G1_Eden_Space avgt 100
>> 933.491 ± 24.164 MB/sec
>> UrlEncoderBenchmark.encodeUtf8:·gc.churn.G1_Eden_Space.norm avgt 100
>> 1555.488 ± 39.204 B/op
>> UrlEncoderBenchmark.encodeUtf8:·gc.churn.G1_Survivor_Space avgt 100
>> 0.006 ± 0.001 MB/sec
>> UrlEncoderBenchmark.encodeUtf8:·gc.churn.G1_Survivor_Space.norm avgt 100
>> 0.010 ± 0.002 B/op
>> UrlEncoderBenchmark.encodeUtf8:·gc.count avgt 100
>> 655.000 counts
>> UrlEncoderBenchmark.encodeUtf8:·gc.time avgt 100
>> 333.000 ms
>
> Looks good.
>
> I wonder... `CharArrayWriter` is an old and synchronized data structure, and
> since the instance used here isn't shared that synchronization seem useless.
> And since you're now bypassing the `char[]` and going straight for a `String`
> you might get better performance with a `StringBuilder` here? (`setLength(0)`
> instead of `reset()`...)
@cl4es hi, let me try `StringBuilder`
-------------
PR: https://git.openjdk.java.net/jdk/pull/1598
