RFR: 8259699: Reduce char[] copying in URLEncoder.encode(String, Charset) [v2]

[Claes Redestad]

On Thu, 14 Jan 2021 09:31:19 GMT, Сергей Цыпанов <github.com+10835776+stsypanov at openjdk.org> wrote:

>> 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 SB brings pessimization both for time and memory, try `org.openjdk.bench.java.net.URLEncodeDecode`:
> master
>                                                  (count)  (maxLength)  (mySeed)  Mode  Cnt         Score       Error   Units
> testEncodeUTF8                                      1024         1024         3  avgt   25         8.573 ?     0.023   ms/op
> testEncodeUTF8:?gc.alloc.rate                       1024         1024         3  avgt   25      1202.896 ?     3.225  MB/sec
> testEncodeUTF8:?gc.alloc.rate.norm                  1024         1024         3  avgt   25  11355727.904 ?   196.249    B/op
> testEncodeUTF8:?gc.churn.G1_Eden_Space              1024         1024         3  avgt   25      1203.785 ?     6.240  MB/sec
> testEncodeUTF8:?gc.churn.G1_Eden_Space.norm         1024         1024         3  avgt   25  11364143.637 ? 52830.222    B/op
> testEncodeUTF8:?gc.churn.G1_Survivor_Space          1024         1024         3  avgt   25         0.008 ?     0.001  MB/sec
> testEncodeUTF8:?gc.churn.G1_Survivor_Space.norm     1024         1024         3  avgt   25        77.088 ?     9.303    B/op
> testEncodeUTF8:?gc.count                            1024         1024         3  avgt   25      1973.000              counts
> testEncodeUTF8:?gc.time                             1024         1024         3  avgt   25       996.000                  ms
> 
> enc
>                                                  (count)  (maxLength)  (mySeed)  Mode  Cnt        Score       Error   Units
> testEncodeUTF8                                      1024         1024         3  avgt   25        7.931 ?     0.006   ms/op
> testEncodeUTF8:?gc.alloc.rate                       1024         1024         3  avgt   25      965.347 ?     0.736  MB/sec
> testEncodeUTF8:?gc.alloc.rate.norm                  1024         1024         3  avgt   25  8430590.163 ?     7.213    B/op
> testEncodeUTF8:?gc.churn.G1_Eden_Space              1024         1024         3  avgt   25      966.373 ?     5.248  MB/sec
> testEncodeUTF8:?gc.churn.G1_Eden_Space.norm         1024         1024         3  avgt   25  8439563.689 ? 47282.178    B/op
> testEncodeUTF8:?gc.churn.G1_Survivor_Space          1024         1024         3  avgt   25        0.007 ?     0.001  MB/sec
> testEncodeUTF8:?gc.churn.G1_Survivor_Space.norm     1024         1024         3  avgt   25       60.949 ?     8.405    B/op
> testEncodeUTF8:?gc.count                            1024         1024         3  avgt   25     1715.000              counts
> testEncodeUTF8:?gc.time                             1024         1024         3  avgt   25      888.000                  ms
> 
> stringBuilder
>                                                  (count)  (maxLength)  (mySeed)  Mode  Cnt         Score       Error   Units
> testEncodeUTF8                                      1024         1024         3  avgt   25         8.115 ?     0.110   ms/op
> testEncodeUTF8:?gc.alloc.rate                       1024         1024         3  avgt   25      1259.267 ?    16.716  MB/sec
> testEncodeUTF8:?gc.alloc.rate.norm                  1024         1024         3  avgt   25  11249391.875 ?     6.552    B/op
> testEncodeUTF8:?gc.churn.G1_Eden_Space              1024         1024         3  avgt   25      1259.937 ?    17.232  MB/sec
> testEncodeUTF8:?gc.churn.G1_Eden_Space.norm         1024         1024         3  avgt   25  11255413.875 ? 43636.143    B/op
> testEncodeUTF8:?gc.churn.G1_Survivor_Space          1024         1024         3  avgt   25         0.007 ?     0.001  MB/sec
> testEncodeUTF8:?gc.churn.G1_Survivor_Space.norm     1024         1024         3  avgt   25        59.461 ?     9.087    B/op
> testEncodeUTF8:?gc.count                            1024         1024         3  avgt   25      2236.000              counts
> testEncodeUTF8:?gc.time                             1024         1024         3  avgt   25      1089.000                  ms
> The reason seems to be single char `StringBuilder.append()` that apart from range check does encoding check and stores `char` as two bytes in `byte[]` in ASB

Surprising, but thanks for checking!

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