apm: Document tail-based sampling performance

[carsonip]

Describe TBS requirements and give some numbers to demonstrate perf overhead.

Numbers are from benchmarks done in elastic/apm-server#11346

Fixes elastic/apm-server#11346

[carsonip]

docs don't like the number of columns

[marclop]

Thanks for the documentation. Only a formatting nit and a correction (I think)

[simitt]

LGTM apart from Marc's comment.

[colleenmcginnis]

Just some minor suggestions below.

[carsonip]

@colleenmcginnis any comment on the table being too wide causing it to be cut off in the UI mentioned in this comment? I can split the apm server version out as a header, but I'm not confident it fixes for all screen sizes

[carsonip]

I've moved the APM server version out as a header

• I'm glad that h4 isn't displayed on the right nav
• It fixes for some screen sizes, not all. If you resize your browser window, sometimes the last column of the table isn't shown

[colleenmcginnis]

Looks good to me! I think the table is ok and the last adjustment you made is a nice strategy to make a little easier to read.

If you have thoughts on how tables could be improved (for example allow control over column widths or making it more obvious that there's hidden content you can scroll left/right to see), please open an issue in https://github.com/elastic/docs-builder.

[carsonip]

Thanks. In that case, I'll double check the numbers in the table and get the PR merged