How to fix the Firefox memory leak

For most users, Firefox doesn't use an abnormally large amount of memory. For others, however, Firefox's memory consumption is a major problem. Typical Firefox memory usage reported by Linux is around 50-100 MB, with virtual memory usage at 100-150 MB. These numbers will vary because Firefox is configured by default to use more memory on systems that have more memory available and less on systems with less.

Firefox memory leak? It doesn’t have one. Unfortunately, because of the way it’s configured to run out of the box it *looks* like it has one.

Follow these simple steps to get your Firefox memory usage under control.

These configuration changes are a trade-off between internet browsing speed and memory usage. They are most useful if you are multitasking and need Firefox to be less of a memory hog while using other applications.

#1: about:config

Type “about:config” into your address bar to access the hidden configuration options for Firefox.

#2: browser.cache.memory.capacity

Controls how much memory is used to cache pages.

Right click on the page and choose New then Integer and create an integer called browser.cache.memory.capacity and set it to a low number. This controls how many kilobytes of memory are used for the browser’s cache.

NOTE: number in screenshot is too small. Aim for 80% of whatever the default is.

#3: browser.cache.disk.capacity

Controls how much disk space is used to cache pages in kilobytes.

Set browser.cache.disk.capacity to between 5000 or 15000.

128MB to 512M -> 5000.
512BM to 1GB of RAM -> use 15000

#4: config.trim_on_minimize (optional)

Configure Firefox to swap memory to disk when minimized. This will make Firefox less responsive if you minimize/maximize a lot, but it is good if you need to free memory while multi-tasking to other applications.

Right click on the page and choose New then Boolean and create a boolean called config.trim_on_minimize and set it to true. Now when you minimize the window it will free up memory.

#5: network.prefetch-next

Network link prefetch will download all pages with the rel=”prefetch” tag. This uses up more memory than you would otherwise think.

Set network.prefetch-next to false.

#6: browser.sessionhistory.max_total_viewers

This controls how many pages of history are kept in the back/forward buttons. Lower the value to something acceptable. If you do not use back/forward often then you can set this very low.
Set browser.sessionhistory.max_total_viewers to a low number.

Once you've done this you should notice a speed improvement on your PC when
using Firefox.

Linux check memory usage:

Linux comes with different command to check memory usage. free command displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel.

vmstat command reports information about processes, memory, paging, block IO, traps, and cpu activity.

Then you can use top command which provides a dynamic real-time view of a running system. It can display system summary information as well as a list of tasks currently being managed by the Linux kernel.

free command

Display free memory size in MB:

$ free -m

Output:

             total       used       free     shared    buffers     cached
Mem:           750        625        125          0         35        335
-/+ buffers/cache:        254        496
Swap:          956          0        956

Displays a line containing the totals memory in MB:

$ free -t -m

Output:

       total       used       free     shared    buffers     cached
Mem:           750        625        125          0         35        335
-/+ buffers/cache:        253        496
Swap:          956          0        956
Total:        1707        625       1082

vmstat command

Type vmstat command at shell prompt:

$ vmstat

Output:

procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
1  0      0 131620  35432 341496    0    0    42    82  737  1364 15  3 81  1

top command

Type top command at shell prompt:

$ top

To exit from top command type q key.

Read man page of free, vmstat, top command for complete information.