1339019 - Add note on performance to Telemetry collection docs

Status: RESOLVED FIXED

(Toolkit :: Telemetry, defect, P1)

Description

[Georg Fritzsche [:gfritzsche]]

Our assumption is that Telemetry is not accumulated from busy/hot loops etc.
Instead we expect users to accumulate locally in those cases and e.g. just Accumulate() the result after.

We should document this expectation explicitly, with notes in histogram, scalar & event docs.

Comment 1

[Chris H-C :chutten]

Attachment: bug 1339019 - Caution against recording Telemetry in hot paths.

Histograms, Scalars, and Events are cheap but not free. Expect performance
impacts if you use them in tight loops or hot paths.

Review commit: https://reviewboard.mozilla.org/r/127272/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/127272/

Comment 2

[Georg Fritzsche [:gfritzsche]]

Comment on attachment 8855426 [details]
bug 1339019 - Caution against recording Telemetry in hot paths.

https://reviewboard.mozilla.org/r/127272/#review130390

Thanks, that looks good enough for now, we can revisit this later if needed.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/852d4ba2bbb2
Caution against recording Telemetry in hot paths. r=gfritzsche

Comment 4

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/852d4ba2bbb2