RFR: 8325730: StringBuilder.toString allocation for the empty String [v3]

[Claes Redestad]

On Tue, 20 Feb 2024 18:42:16 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> JDK-8282429 accidentally removed an optimization (JDK-8240094) that ensured StringBuilder/StringBuffer::toString returns `""` when the builders are empty.
>> 
>> 
>> Name                         Cnt     Base      Error   Test   Error   Unit  Change
>> StringBuffers.emptyToString    5   12,289 ±    0,384  9,883 ± 0,721  ns/op   1,24x (p = 0,000*)
>>   :gc.alloc.rate                 1862,398 ±   57,647  0,007 ± 0,000 MB/sec   0,00x (p = 0,000*)
>>   :gc.alloc.rate.norm              24,000 ±    0,000  0,000 ± 0,000   B/op   0,00x (p = 0,000*)
>>   :gc.count                        31,000             0,000         counts
>>   :gc.time                         21,000                               ms
>> StringBuilders.emptyToString   5    4,146 ±    0,567  0,646 ± 0,003  ns/op   6,42x (p = 0,000*)
>>   :gc.alloc.rate                 9208,656 ± 1234,399  0,007 ± 0,000 MB/sec   0,00x (p = 0,000*)
>>   :gc.alloc.rate.norm              40,000 ±    0,000  0,000 ± 0,000   B/op   0,00x (p = 0,000*)
>>   :gc.count                        96,000             0,000         counts
>>   :gc.time                         64,000                               ms
>>   * = significant
>
> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Revert accidental import

Thanks!

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PR Comment: https://git.openjdk.org/jdk/pull/17931#issuecomment-1955020047