Result of  bench.py attached to issue #25267: attached bench_utf8_result.txt.

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Summary                                               | utf8_before |     utf8_after
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ignore: "\udcff" * length                             | 7.63 us (*) |        7.91 us
ignore: "a" * length + "\udcff"                       | 10.7 us (*) |        10.8 us
ignore: ("a" * 99 + "\udcff" * 99) * length           | 2.17 ms (*) |        2.16 ms
ignore: ("\udcff" * 99 + "a") * length                |  843 us (*) |         866 us
ignore: "\udcff" + "a" * length                       | 10.7 us (*) |          11 us
replace: "\udcff" * length                            | 7.87 us (*) |  8.43 us (+7%)
replace: "a" * length + "\udcff"                      | 10.8 us (*) |        10.9 us
replace: ("a" * 99 + "\udcff" * 99) * length          | 2.46 ms (*) |        2.46 ms
replace: ("\udcff" * 99 + "a") * length               |  907 us (*) |         939 us
replace: "\udcff" + "a" * length                      | 10.9 us (*) |          11 us
surrogateescape: "\udcff" * length                    | 14.2 us (*) | 17.2 us (+21%)
surrogateescape: "a" * length + "\udcff"              | 10.6 us (*) |        10.7 us
surrogateescape: ("a" * 99 + "\udcff" * 99) * length  | 3.19 ms (*) |   3.4 ms (+7%)
surrogateescape: ("\udcff" * 99 + "a") * length       | 1.64 ms (*) | 1.87 ms (+13%)
surrogateescape: "\udcff" + "a" * length              | 10.6 us (*) |        10.7 us
surrogatepass: "\udcff" * length                      | 23.1 us (*) |        23.5 us
surrogatepass: "a" * length + "\udcff"                | 10.7 us (*) |        10.8 us
surrogatepass: ("a" * 99 + "\udcff" * 99) * length    | 4.39 ms (*) |        4.44 ms
surrogatepass: ("\udcff" * 99 + "a") * length         | 2.43 ms (*) |        2.47 ms
surrogatepass: "\udcff" + "a" * length                | 10.6 us (*) |        10.8 us
backslashreplace: "\udcff" * length                   | 65.7 us (*) |        64.3 us
backslashreplace: "a" * length + "\udcff"             | 15.7 us (*) |          15 us
backslashreplace: ("a" * 99 + "\udcff" * 99) * length |   12 ms (*) | 15.9 ms (+32%)
backslashreplace: ("\udcff" * 99 + "a") * length      | 11.1 ms (*) | 13.5 ms (+22%)
backslashreplace: "\udcff" + "a" * length             | 16.4 us (*) |  15.1 us (-8%)
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Total                                                 | 41.4 ms (*) | 48.3 ms (+17%)
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