[R] Documentation for threading could be improved

[paleolimbot]

Describe the enhancement requested

After https://github.com/apache/arrow/pull/36304?notification_referrer_id=NT_kwDOAKfIMrM2ODgwMjA4ODQ3OjEwOTk1NzYy#issuecomment-1608564686 , which had excellent suggestions on how to improve the documentation around threading/concurrency and where to change the options. Notably:

• We could probably unify the io/cpu thread man pages and take the opportunity to explain the difference between them (linking to https://arrow.apache.org/docs/cpp/threading.html for more details)
• Where these values matter, we should link to that man page. Notably, the performance of read_csv_arrow(), read_parquet(), and arrow/dplyr are affected by the number of available threads.

@tdhock Let me know if I characterized any of these or if you have more suggestions!

Component(s)

R

[paleolimbot]

I'll do my best to follow up on this before the next release...if you feel motivated it's also a great first issue 🙂 .

[tdhock]

yes that would be great thanks.

[tdhock]

(I don't know enough about how arrow works to contribute a fix/pr though)