`memchr` vs `stringzilla` performance comparison

[RoloEdits]

Came across a benchmarking comparison between the two.

Notably the results:

	ASCII ⏩	ASCII ⏪	UTF8 ⏩	UTF8 ⏪
Intel:
memchr	5.89 GB/s	1.08 GB/s	8.73 GB/s	3.35 GB/s
stringzilla	8.37 GB/s	8.21 GB/s	11.21 GB/s	11.20 GB/s
Arm:
memchr	6.38 GB/s	1.12 GB/s	13.20 GB/s	3.56 GB/s
stringzilla	6.56 GB/s	5.56 GB/s	9.41 GB/s	8.17 GB/s
Average	1.2x faster	6.2x faster	-	2.8x faster

Its noted that that rust crate doesn't cover the full c++ api, but that it is planned to do so eventually. In the interest of performance, I thought I would share the benchmark results so informed exploring can be done if desired, if the potential gains match up with any wins for one crate or the other.

[Mingun]

Very interesting! If I understand correctly, this is results of benchmarks of crates themselves, you didn't integrate stringzilla to quick-xml, right? I'm always open in performance improvements so if you will you can create a PR with a replacement so everyone can experiment with such change. Note, however, that these results probably from searching small patterns in long strings. XML usually has a different access pattern -- many searches of small patterns in small strings. As you can see from quick-xml self benchmarks, the maybe_xml is even faster than quick-xml in most cases, although it does not use any SIMD libs. quick-xml wins only on very long XMLs (several megabytes) which, I think, usually a rare case.

[dralley]

BurntSushi provided a response on Reddit, it seems like the benchmarks are a bit misleading, there are some circumstances in which StringZilla is faster but on average it seems to be slower.

https://www.reddit.com/r/rust/comments/1ayngf6/memchr_vs_stringzilla_benchmarks_up_to_7x/