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See the following Force Quit popup message:

Your system has run out of application memory.

Your system has run out of application memory

Firefox uses 57GB memory, the other apps use only 1% of that. I've seen this many times (>10) by now, and it's always around 55-57GB. The internal SSD has 25GB available, the system has 8GB RAM. I don't know how it can use 57GB because that is not available.

This message results in macOS killing several apps automatically. Strangely Firefox is not killed. I have to do that myself. Yesterday this happened, two days ago, but most of the time it's not that often.

Below you see the current memory usage, with Firefox using almost 9GB, and the webcontent/extensions using another 6GB, so 15GB together. I started FF about two hours ago.

Today I disabled a lot of addons, but I don't see any improvement.

Activity Monitor

Questions

  • What is going on here?
  • How can I see what is causing this problem?
  • How can a system claim this much memory while it is not available?
3
  • What tab/site crashes when you kill the large Web Content subprocess?
    – Daniel B
    Apr 30, 2019 at 17:54
  • The tabs don't crash. It's the OS taking over and closing other applications because of the memory use.
    – SPRBRN
    May 1, 2019 at 10:29
  • No, that’s not what I am asking. I am asking you to kill the large Web Content process to see what effect this has on the browser.
    – Daniel B
    May 1, 2019 at 11:38

2 Answers 2

1

To see what processes are actually children of Firefox, go to Activity Monitor, View menu > All Processes Hierarchically, then sort by Memory not Name, so the heavy-hitters come to the top. Everything will be a child of kernel_task, then launchd, but you can further expand the list.

Very few processes will be named after the viewer, they will mainly be named after the http resource name.

Check which is using the most, & add up all the individual entries to make sure they roughly tally with the overall figure you quoted.
Unless you've got 100 tabs open, you may find just one or two runaway processes, which ought to be conveniently named after their web site, so you can find & close them.

enter image description here

3
  • Using "All Processes Hierarchically", I don't see more processes, and all are under my name. This is a Mac, not Linux. I don't see which tab (domain) is used by which process. I did however close tabs, and two of them were using 5GB each. One was not so surprisingly an only tutorial/editor, so lots of javascript, the other was a news paper with nothing much going on, no video or animations. And I tend to keep some of these tabs open for days, so maybe that results in a built up? I'm going to monitor this.
    – SPRBRN
    Apr 30, 2019 at 14:56
  • Picture added - big enough to see, not big enough to read. That's how much I've got open in Safari right now. I have no idea why you think I'm talking about Linux....
    – Tetsujin
    Apr 30, 2019 at 15:49
  • (Sorry I misread your reply. You mentioned the "http resource name", and I read it as http as process owner. That's still no reason to think this is Linux, but let's say I was tired.) I see no resource name. Your screenshot shows Safari with indeed domain names. Firefox doesn't have this. I've been playing with the columns in the Activity Monitor, and now see "Real Memory" which is much lower (530MB) than "Memory" (10GB currently).
    – SPRBRN
    May 1, 2019 at 10:01
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Firefox using more memory that exists on the computer, means that some of its allocated memory was swapped out to disk. Swapping back and forth might slow Firefox down, but if you don't see such slowing then probably this memory was allocated and then forgotten and is not used any more.

To see what memory is Firefox allocating, go to about:memory, which may look similar to:

enter image description here

You may use the button "Measure and save..." to save a report on the usage of memory by Firefox. If you do that when Firefox is using an extensive amount of memory, then posting the saved report will help us analyze it.

You may also use the button "Minimize memory usage" to immediately release all allocated memory. Let us know if this effectively fixed the problem for the moment and did reduce the memory used by Firefox. If it works, this can be a temporary solution to the problem.

Some questions relating to your environment:

  1. Do you have lots of tabs open when this happens?
  2. Does this happen if you disable all your add-ons (or almost all)?
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  • I don't restart my computer for weeks if possible, leaving Firefox open without restarting, and leaving some tabs open all the time. Maybe memory adds up somehow on these tabs? I'm not trying to go back to closing all tabs daily, and see if that changes things. If it happens again, I'll try this method. Still I'm confused how writing memory to disk can happen for 57GB if RAM + free disk space < 33GB?
    – SPRBRN
    May 1, 2019 at 10:06
  • This might indicate some memory leak in Firefox itself or some add-on. The memory dump can serve for us here to analyze, or for a bug report if you have found a new bug.
    – harrymc
    May 1, 2019 at 10:10

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