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

[Сергей Цыпанов]

On Sun, 10 Jan 2021 20:13:51 GMT, Attila Szegedi <attila 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!

@szegedi could you please create a ticket for this change? Otherwise I cannot merge it

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