1914762 - Firefox low memory mamanagement needs work.

Status: UNCONFIRMED

(Core :: Performance, defect)

Description

[David]

User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:109.0) Gecko/20100101 Firefox/115.0

Steps to reproduce:

Run the browser for an extended period of time with browser.low_commit_space_threshold_mb set to a custom value of 12261 on a system with 8192 MB of RAM. Allowed memory use to climb to a point where it should begin shedding tabs to bring memory use into compliance.

Actual results:

Tab unloading occurs too late, as it appears the custom value set for browser.low_commit_space_threshold_mb is ignored. Unloading appears to occur only after dipping below around 400 MB, despite customizing this value.

Expected results:

Value set for browser.low_commit_space_threshold_mb should actually be followed, so tabs will begin unloading based on the amount set.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Firefox::Tabbed Browser' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[David]

Correction: 13453 MB is the custom value used. It is my understanding that this would cause tab unloading to engage, if the committed memory exceeds 7000 MB based on this.

Comment 3

[David]

It appears this configuration parameter does not have any effect if Fission is in use. I'm not sure if that's intentional or not, but I've been able to confirm that no tab unloading takes place with this in use, by artificially setting the threshold to a number just slightly higher than the actual commit limit. I then open a new tab to about:unloads and refresh constantly to verify it's not unloading.

Comment 4

[David]

I've been continuing to experiment with this. It seems there would be a performance benefit to bypassing the low memory call from Windows. Performance and tab unloading would function better if Firefox had it's own customizable threshold that was based on available physical memory. The goal should be to prevent the browser from driving the workstation to page to disk. For example: on an 8 GB system, it would start unloading tabs at 7 GB usage.

Comment 5

[BugBot [:suhaib / :marco/ :calixte]]

This bug was moved into the Performance component.

:confidentblast, could you make sure the following information is on this bug?

• For slowness or high CPU usage, capture a profile with http://profiler.firefox.com/, upload it and share the link here.
• For memory usage issues, capture a memory dump from about:memory and attach it to this bug.
• Troubleshooting information: Go to about:support, click "Copy raw data to clipboard", paste it into a file, save it, and attach the file here.

If the requested information is already in the bug, please confirm it is recent.

Thank you.

Comment 6

[David]

Attachment: Memory measurment

Comment 7

[Frank Doty [:fdoty]]

Removing perf impact flag and adding to memory investigation meta bu - please continue to provide additional details to help us remedy any possible issues