732053 - make linear histograms harder to get wrong

Status: RESOLVED FIXED

(Toolkit :: Telemetry, defect)

Description

[Nathan Froyd [:froydnj]]

Due to a quirk (?) in linear histograms, if you want a histogram with a single bucket for each value in 1..N, you need to declare it:

HISTOGRAM(NAME, 1, N, N+1, LINEAR, EXPLANATION)

and not:

HISTOGRAM(NAME, 1, N, N, LINEAR, EXPLANATION)

because you need to account for the implicit zero bucket at the bottom.

This has come up a couple times for new histograms, and at least GC_REASON seems to suffer from a wrong declaration.  SSL telemetry was/is going to use histograms like this, too.

Comment 1

[Nathan Froyd [:froydnj]]

Attachment: patch

The dead simple patch.  Bikeshedding about the name welcome.

Comment 2

[Nathan Froyd [:froydnj]]

Histograms that could benefit from this macro:

GC_REASON
HTTP_*_DISPOSITION
CACHE_*_SEARCH (odd to have a linear histogram for ms histogram, especially one so finely bucketed)
CACHE_SERVICE_LOCK_WAIT* (same)
PLACES_EXPIRATION_STEPS_TO_CLEAN
DNS_LOOKUP_METHOD
UPDATE_STATUS

but most of those would involve a small tweak to the histogram (either in # of buckets or upper bound); doesn't seem worth the effort

Comment 3

[(dormant account)]

Comment on attachment 604111 [details] [diff] [review]
patch

HISTOGRAM_SINGLE_VALUE_BUCKET is the best you can come up with?  How about HISTOGRAM_CONTINUOUS?

Comment 4

[Nathan Froyd [:froydnj]]

HISTOGRAM_CONTINUOUS doesn't sound right.  HISTOGRAM_ENUMERATED_VALUES (since most people seem to be sticking enums in these anyway)?

Comment 5

[(dormant account)]

(In reply to Nathan Froyd (:froydnj) from comment #4)
> HISTOGRAM_CONTINUOUS doesn't sound right.  HISTOGRAM_ENUMERATED_VALUES
> (since most people seem to be sticking enums in these anyway)?

r+

Comment 6

[Nathan Froyd [:froydnj]]

Attachment: patch

Use HISTOGRAM_ENUMERATED_VALUES.  Adding r+ per Taras's earlier comment.

Comment 7

[Mozilla RelEng Bot]

Autoland Patchset:
	Patches: 606203
	Branch: mozilla-central => try
	Destination: http://hg.mozilla.org/try/pushloghtml?changeset=a9acecdb826d
Try run started, revision a9acecdb826d. To cancel or monitor the job, see: https://tbpl.mozilla.org/?tree=Try&rev=a9acecdb826d

Comment 8

[Mozilla RelEng Bot]

Try run for a9acecdb826d is complete.
Detailed breakdown of the results available here:
    https://tbpl.mozilla.org/?tree=Try&rev=a9acecdb826d
Results (out of 14 total builds):
    success: 14
Builds (or logs if builds failed) available at:
http://ftp.mozilla.org/pub/mozilla.org/firefox/try-builds/[e-mail]-a9acecdb826d

Comment 9

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/da0a5a4b0519

Comment 10

[Marco Bonardo [:mak]]

https://hg.mozilla.org/mozilla-central/rev/da0a5a4b0519