So, in one of the Firefox tabs, I typed about:memory, which displays memory-related options, one of which is to "Minimize memory usage". If you have the mouse pointer over the button for that option, you will see the following (image):
Send three "heap-minimize" notifications in a row. Each notification triggers a global garbage collection followed by a cycle collection, and causes the process to reduce memory usage in other ways, e.g., by flushing various caches.
So I clicked on that buton. I saw a "Memory minimization completed" message in the about:memory window and the Windows Task Manager showed a reduction of memory usage, which had been fairly constant at about 849 MB, fluctuating from 849.1 to 849.5, reduced to 802.3 MB.
I clicked on the "Mimimize memory usage" button again, which reduced the memory usage briefly to about 795 MB, but then it went back up, going up to about 809 MB, though it was still about 90 MB less than it had been before I first clicked on the button, though the memory usage percentage was only down slightly at 47%.
So, you may be able to reduce Firefox's memory usage somewhat when high memory usage is causing a problem in the system's performance, but it won't always be a panacea when you wish to reduce the browser's memory usage considerably.
I next clicked on the Measure button on the about:memory page. I saw that a Googe Docs page I had open was at the top of the list for "Explicit Allocations", so I used the back button on that tab to go back to a page open before that and then a page on my own site appeared at the top of "Explicit Allocations" as using about 38 MB of memory (image). Task Manager was showing the memory usage fluctating between 834 MB and 844 MB at the time, though I had closed several tabs since I had reduced memory usage by the "Miminize memory usage" option. After I closed the tab that was shown at the top of the "Explict Allocations" list the usage dropped to about 810 MB. CPU usage was down to about 3% at that time and I no longer had a performance problem. When I clicked on the Measure buton in the about:memory window again, it showed 652.77 MB, instead of the 683.80 MB figure it had previously shown (image).
So, if you are seeing high memory consumption by Firefox, put about:memory in the address bar of a tab and try the "Reduce memory usage" option. If that doesn't sufficiently reduce memory, try the "Measure" option to view memory usage by Firefox. Hopefully those steps will allow you to reduce Firefox's memory consumption enough to alleviate the problem.
Created: January 17, 2016
