RFR: 8259699: Reduce char[] copying in URLEncoder.encode(String, Charset)

[Attila Szegedi]

On Thu, 3 Dec 2020 14:29:58 GMT, Сергей Цыпанов <github.com+10835776+stsypanov at 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!

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Marked as reviewed by attila (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1598