RFR: 8305811: (bf) Improve performance of CharBuffer::append(CharSequence[,int,int]) [v4]

[Brian Burkhalter]

On Fri, 14 Apr 2023 00:41:59 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> I'll check it out.
>
> The commit bf403f90bce165ad71e45a0372d22be4165c3e61 adds the use of `getChars()` when appending a subsequence of a `String` or `StringBuffer`. Avoiding substring allocation in fact improves performance as shown in these updated results:
> 
> Benchmark                                 Mode  Cnt        Score        Error  Units
> CharBufferAppend.appendDirectToDirect    thrpt   10  4719216.266 ± 227330.627  ops/s
> CharBufferAppend.appendDirectToHeap      thrpt   10  2102880.055 ±  55054.002  ops/s
> CharBufferAppend.appendHeapToDirect      thrpt   10  2328149.744 ± 110434.431  ops/s
> CharBufferAppend.appendHeapToHeap        thrpt   10  3227172.246 ±  79850.461  ops/s
> CharBufferAppend.appendString            thrpt   10  4418599.392 ±  51612.735  ops/s
> CharBufferAppend.appendStringBuffer      thrpt   10  4362670.418 ± 101017.472  ops/s
> CharBufferAppend.appendStringBuilder     thrpt   10  3856127.917 ± 110625.008  ops/s
> CharBufferAppend.appendSubString         thrpt   10  7913540.253 ±  84487.457  ops/s
> CharBufferAppend.appendSubStringBuffer   thrpt   10  8284545.161 ± 102884.827  ops/s
> CharBufferAppend.appendSubStringBuilder  thrpt   10  8258542.262 ±  94236.638  ops/s```

The commit message of https://github.com/openjdk/jdk/commit/bf403f90bce165ad71e45a0372d22be4165c3e61 should have been "8305811: Use getChars() when appending a partial String or StringBuffer."

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PR Review Comment: https://git.openjdk.org/jdk/pull/13415#discussion_r1166162487