task manager

well in safe mode

More than one process is normal for the current Firefox. http://www.ghacks.net/2016/07/22/multi-process-firefox/

Multi-process Firefox is codenamed "e10s". https://wiki.mozilla.org/Firefox/multiprocess

well in safe mode

Does that mean the problem is gone in Safe Mode?

It could be the work of one of your add-ons, or it could be Hardware Acceleration. How to disable Hardware Acceleration {web link}

Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; <Control> (Mac=<Command>) <Shift> A)

In the Add-ons Manager, on the left, select Extensions. Disable a few add-ons, then Restart Firefox.

Some added toolbar and anti-virus add-ons are known to cause Firefox issues. Disable All Of them.

If the problem continues, disable some more (restarting FF). Continue until the problem is gone. After, you know what group is causing the issue. Re-enable the last group ONE AT A TIME (restarting FF) until the problem returns.

Once you think you found the problem, disable that and re-enable all the others, then restart again. Let us know who the suspect is, detective.

Hello FredMcD!

Thanks for your response!

I havetried Safe mode + disable hardware acceleration and FF only uses 220MB memory (1 tab with about:memory) (It is the first time firefox use that less memory). It's happy to see it but I think it still didn't solve my confusion.

As I said before, my friend's FF uses ONLY 180MB memory with no safe mode + have hardware acceleration + have some add-ons enabled. Firefox memory footprint is a bit frustrating for me because chrome uses less memory than firefox on my laptop!

I also tried out firefox nightly and it starts with around 400MB memory usage. It seems that the problem is about my system not firefox. I set my virtual memory to 8GB (not on C: drive) and 400MB in C: drive before, is this possible to make firefox allocate more physical memory?

Sorry for my inappropriate grammar and the unorganized passage. Thanks for your help!

also a question: in my task manager firefox has 6 processes (has 5 after disabling hardware acceleration) but in my friend's case he has only 4. how?

also a question: in my task manager firefox has 6 processes but in my friend's case he has only 4. how?

The processes other than firefox on the task manager are the processes for the addons

Basically, an OOM (Out Of Memory) means the system is having issues with the RAM.

https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster

https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix

https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-ram

https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding

https://support.mozilla.org/en-US/kb/firefox-takes-long-time-start-up

https://support.mozilla.org/en-US/kb/quick-fixes-if-your-firefox-slows-down

MemTest LAST UPDATED : 12/04/2020 Could you please run a tool from http://memtest.org/ in order to check the integrity of your RAM?

You will need a thumb or disk drive to install it on.

Do you let Windows handle the page file or did you set a fixed size ? If you use a fixed size for the page file then try the former and let Windows handle the page file. How to determine the appropriate page file size for 64-bit versions of Windows {web link}