1657188 - Add probes equivalent to TIME_TO_LOAD_EVENT_{START,END}_MS for loads with rel=preload and without

Status: RESOLVED FIXED

(Core :: Performance, task, P2)

Description

[Beth Rennie [:beth] (she/her)]

We want to be able to compare load times with rel=preload enabled vs disabled, so we need a metric that is identical to TIME_TO_LOAD_EVENT_END except only triggered when the network.preload pref is set to true and the document contained a <link rel=preload> tag.

Comment 1

[Beth Rennie [:beth] (she/her)]

Four probes should be added:

• TIME_TO_LOAD_EVENT_START_REL_PRELOAD_MS: identical to TIME_TO_LOAD_EVENT_START_MS, but only reported if network.preload=true and the document tree contained a document with a <link rel=preload> element.
• TIME_TO_LOAD_EVENT_END_REL_PRELOAD_MS: identical to TIME_TO_LOAD_EVENT_END_MS, but only reported if network.preload=true and the document tree contained a document with a <link rel=preload> element.
• TIME_TO_LOAD_EVENT_START_NO_REL_PRELOAD_MS: identical to TIME_TO_LOAD_EVENT_START_MS, but only reported if network.preload=false or the document tree did not contain a document with a <link rel=preload> element.
• TIME_TO_LOAD_EVENT_END_NO_REL_PRELOAD_MS: identical to TIME_TO_LOAD_EVENT_END_MS, but only reported if network.preload=false or the document tree did not contain a document with a <link rel=preload> element.

Comment 2

[Honza Bambas (:mayhemer)]

To slightly adjust the condition - instead of "the document tree contained a document with a <link rel=preload> element" use "the document preloaded a resource." Because there is also the Link: header and scripts may add <link preload> tags dynamically.

This is easy to detect, we need a new flag in PreloadService (exposed as a public member on dom::Document) that it has preloaded a resource (that it has got at this spot). I'm not 100% sure about dom::Document reuse, but there should always be a new instance for a new page load, AFAIK, so no need to reset the flag. With this you don't need to check the network.preload=true pref.

Comment 3

[Beth Rennie [:beth] (she/her)]

Attachment: data-collection.md

Comment 4

[Beth Rennie [:beth] (she/her)]

Attachment: Bug 1657188 - Implement rel=preload load time telemetry r?nika!,emilio!,smacleod

Comment 5

[Chris H-C :chutten]

Comment on attachment 9168277 [details]
data-collection.md

DATA COLLECTION REVIEW RESPONSE:

Is there or will there be documentation that describes the schema for the ultimate data set available publicly, complete and accurate?

Yes.

Is there a control mechanism that allows the user to turn the data collection on and off?

Yes. This collection is Telemetry so can be controlled through Firefox's Preferences.

If the request is for permanent data collection, is there someone who will monitor the data over time?

No. This collection will expire in Firefox 88.

Using the category system of data types on the Mozilla wiki, what collection type of data do the requested measurements fall under?

Category 1, Technical.

Is the data collection request for default-on or default-off?

Default on for all channels.

Does the instrumentation include the addition of any new identifiers?

No.

Is the data collection covered by the existing Firefox privacy notice?

Yes.

Does there need to be a check-in in the future to determine whether to renew the data?

Yes. Barret Rennie is responsible for renewing or removing the collection before it expires in Firefox 88.

---

Result: datareview+

Comment 6

[Kim Moir [:kmoir] ET]

Triaging performance - Barret could you please set a priority and severity on this bug?

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/643f16da7b99
Implement rel=preload load time telemetry r=Dexter,emilio,nika

Comment 8

[Razvan Maries]

Backed out for perma failures.

See https://bugzilla.mozilla.org/show_bug.cgi?id=1663963#c3

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/dc8d6a216ffa
Implement rel=preload load time telemetry r=Dexter,emilio,nika

Comment 10

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/dc8d6a216ffa