1632880 - High process overhead when number of tabs = number of processes

Status: RESOLVED DUPLICATE of bug 1436250

(Core :: DOM: Content Processes, defect)

Description

[Julien L.]

Attachment: high_ram_usage_ff_75_vs_edge_81.jpg

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:75.0) Gecko/20100101 Firefox/75.0

Steps to reproduce:

I simply browsed the web and opened a few tabs, then closed them.

I would like in this report to alarm you about the fact that Firefox x64 (in Windows 10) uses a lot of RAM, comparing to Edge and Chrome.

Actual results:

The memory used grew up to 1.1 GB, with only 4 normal tabs active.
You can compare Firefox and Edge Chromium with my screenshot (with 4 active tabs).

Expected results:

Firefox should use less RAM.

Comment 1

[Julien L.]

Attachment: high_ram_usage_ff_75.jpg

Comment 2

[Julien L.]

Please note that I used 8 content processes during my tests.

Comment 3

[Julien L.]

Attachment: ff75_cpu_and_ram_usage_after_1_hour.jpg

Firefox 75.0, with 6 content processes only, had some buggy behavior : it took a lot of RAM, and a bit of CPU for nothing. I was just browsing a web store (www.fnac.com).

Comment 4

[Andrei Purice]

Salut Julien,

I can reproduce this with 77.0a1 (2020-04-29), beta 76.0 and release 75.0. Indeed opening 9 tabs at least gets the memory usage up to 1gb. I had nothing else installed during this test - no addons, themes, etc.

Adding a component for this issue in order to get the dev team involved.
Please feel free to change it if it's not correct to a more appropriate one.

Comment 5

[Julien L.]

Attachment: I can add an about:memory report (4 tabs opened, 8 max. content processes, 0 webextensions).

Comment 6

[Julien L.]

Attachment: memory_performance_report

I can also add a report of the developpers tool of Firefox 75.0.

Comment 7

[Andrew McCreight [:mccr8]]

Memory allocator isn't going to be the correct component for high memory usage except in unusual circumstances.

Comment 8

[Andrew McCreight [:mccr8]]

Looking at resident-unique from the memory report, the various smaller processes use 240mb total, Web Content (pid 1892) uses 390mb and the main process uses 176mb (380mb resident). The basic problem here is that Firefox's content process overhead is higher than other browsers. Opening 6 to 8 tabs is kind of the worst case scenario for comparing memory usage to other browsers, which have lower per-process overhead but will keep using more content processes beyond 8 (to provide improved security).

Firefox looks particularly bad with this set of pages, because aside from fnac.com the pages that are open are small, so process overhead is dominating the total memory usage.

It might be possible in the short term to improve our memory usage in this particular scenario by not using additional content processes until we've decided that the existing ones are being well-utilized, but we are in the midst of trying to ship Project Fission, which will require that we have a new process for every domain, so our effort would probably be better spent reducing process overhead, so I'm going to dupe this bug to the meta bug we have filed for that.