Remove predictor code

👁 Image	Valentin Gosu [:valentin] Assignee
	Description • 6 months ago

The predictor was completely disabled recently, and in many cases it slowed down the browser. Most of its functionality was never enabled by default.
With Early hints and speculation rules, most of what the predictor tried to achieve can be done by web developers, instead of the browser trying to guess it.

👁 Image	Valentin Gosu [:valentin] Assignee
	Comment 1 • 6 months ago

The network predictor used the HTTP cache as a database to learn browsing
patterns and make speculative DNS prefetches, TCP preconnects, and resource
prefetches. While this provided performance benefits for repeat visits to
frequently-accessed sites, it came with significant costs: I/O on every page
load, CPU overhead for prediction algorithms, memory for caching learned
patterns, and substantial IPC complexity with six message types coordinating
predictions between processes.

A large part of the functionality the predictor was meant to improve is now
available to webdevelopers. HTTP 103 Early Hints allow servers to explicitly
specify resources to preload while generating the response.
And Speculation Rules API will enable content authors to declaratively specify
prefetch/prerender behavior based on their knowledge of site structure and user
intent, providing immediate accuracy without a learning period.

The network.predictor.enable-hover-on-ssl preference is retained as it controls
simpler hover-triggered speculative connections that don't require the
predictor's learning system. This removal simplifies the codebase while
steering users toward more accurate, standards-based optimization mechanisms.

The one feature of the predictor which was never used was learning websites
that are opened soon after startup. There was no action taken based on this
info, and we could already predict this info based on the history database.

👁 Image	Pulsebot
	Comment 2 • 6 months ago

Pushed by valentin.gosu@gmail.com: https://github.com/mozilla-firefox/firefox/commit/117ed7db9907 https://hg.mozilla.org/integration/autoland/rev/4d434e20a9d0 Remove predictor code r=necko-reviewers,firefox-style-system-reviewers,emilio,kershaw

👁 Image	Pulsebot
	Comment 3 • 6 months ago

Pushed by abutkovits@mozilla.com: https://github.com/mozilla-firefox/firefox/commit/79e1b8910963 https://hg.mozilla.org/integration/autoland/rev/00ab0a5bf088 Revert "Bug 2006028 - Remove predictor code r=necko-reviewers,firefox-style-system-reviewers,emilio,kershaw" for causing failures at test_basic.js.

👁 Image	Atila Butkovits
	Comment 4 • 6 months ago • Edited

Backed out for causing failures at test_basic.js.

Backout link: https://hg-edge.mozilla.org/integration/autoland/rev/00ab0a5bf088ed71b8c42083b4a0684d4b277fe4

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=4d434e20a9d03156d0e012425b30c8aa9d3066e1&selectedTaskRun=dm8cfhyfQ4uSy9wa7qNbLw.0

Failure logs:
https://treeherder.mozilla.org/logviewer?job_id=540251252&repo=autoland&task=dm8cfhyfQ4uSy9wa7qNbLw.0&lineNumber=3087
https://treeherder.mozilla.org/logviewer?job_id=540250035&repo=autoland&task=BS44lchfTyKw66exJzMFsQ.0&lineNumber=5797
https://treeherder.mozilla.org/logviewer?job_id=540253041&repo=autoland&task=OLf5Pyj7TYucB661iszZnw.0&lineNumber=26009

👁 Image	Valentin Gosu [:valentin] Assignee
	Updated • 6 months ago

👁 Image	Gregory Pappas [:gregp]
	Comment 5 • 6 months ago

These prefs are removed:

• network.predictor.enabled
• network.predictor.enable-prefetch
• network.predictor.page-degradation.day
• network.predictor.page-degradation.week
• network.predictor.page-degradation.month
• network.predictor.page-degradation.year
• network.predictor.page-degradation.max
• network.predictor.subresource-degradation.day
• network.predictor.subresource-degradation.week
• network.predictor.subresource-degradation.month
• network.predictor.subresource-degradation.year
• network.predictor.subresource-degradation.max
• network.predictor.prefetch-rolling-load-count
• network.predictor.prefetch-min-confidence
• network.predictor.preconnect-min-confidence
• network.predictor.preresolve-min-confidence
• network.predictor.prefetch-force-valid-for
• network.predictor.max-resources-per-entry
• network.predictor.max-uri-length
• network.predictor.doing-tests

👁 Image	Pulsebot
	Comment 6 • 6 months ago

Pushed by valentin.gosu@gmail.com: https://github.com/mozilla-firefox/firefox/commit/44bd5382c062 https://hg.mozilla.org/integration/autoland/rev/bcf58080cea5 Remove predictor code r=necko-reviewers,firefox-style-system-reviewers,emilio,kershaw,extension-reviewers,toolkit-telemetry-reviewers,manuel,robwu

👁 Image	Sandor Molnar[:smolnar]
	Comment 7 • 6 months ago
bugherder

https://hg.mozilla.org/mozilla-central/rev/bcf58080cea5

👁 Image	Camelia Badau [:cbadau], Desktop Test Engineering
	Updated • 5 months ago