1384857 - Nested iframe memory leak with external javascript

Status: RESOLVED INCOMPLETE

(Core :: DOM: Core & HTML, defect, P5)

Description

[M. van Egmond]

Attachment: Zipfile with screenshot and testcase

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:54.0) Gecko/20100101 Firefox/54.0
Build ID: 20170628075643

Steps to reproduce:

For a business application we have many nested iframes. We've noticed that Firefox has been using more memory than normal. It seems that Firefox never cleans detached iframes, especially when having iframes inside iframes. This gives huge memory problems for sites with nested iframes. We've been able to pin it down to iframes in combination with an external javascript. Iframes with only inline javascript have no problems.
Eventually Firefox starts eating up all available RAM because every frame takes up 1,5 to 50 MB (depending on how many resources are loaded inside the iframe).
I have attached a testcase and a couple of screenshots. In my testcase the resources leaked are not that much because hardly any are loaded.




Actual results:

Open a page with iframes, or even iframes inside iframes. Create a javascript to remove the iframe from the DOM or navigate the main iframe to a new page. The removed or child iframes will not be garbage collected. Even if GC and CC are forced by using about:memory.
Doing exactly the same for an iframe without external javascripts have no problem and are nicely GC'd. Firefox will only GC the detached windows when the top level window is navigated away or closed. This is impossible with big enterprise portal pages which use iframes etc.
Funny thing is that Firefox will only keep one zombie iframe when you use the same URL. Therefore the testcase adds something random to each URL.


Expected results:

All (nested) iframes should be removed from memory upon navigating away or removal from the DOM, not only iframes without external javascripts.

Comment 1

[M. van Egmond]

Tested on Win10 64bit and 32bit and Ubuntu 64bit with Firefox 54. Same results.

Furthermore in the testcase if you sequencely keep spamming "Create Iframes with external js" and then "Step 2: cleanup iframes" you'll clearly see RAM usage ramping up. This memory will not be released, until you navigate the toplevel window elsewhere or close it. In some cases zombie windows even keep existing until Firefox is closed.

Comment 2

[Jon Coppeard (:jonco)]

Andrew, this sounds like it could be a DOM issue.  Any thoughts?

Comment 3

[Andrew McCreight [:mccr8]]

Yeah, it sounds like a ghost window kind of issue. I'll take a look next week.

Comment 4

[Andrew McCreight [:mccr8]]

Sorry for the very long delay before anybody looked at this. I am unable to reproduce this issue using your test case in Firefox 57. Can you reproduce this in more recent versions, such as 55? Do you have any addons installed, or is this a fresh profile?