Firefox on RAM

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Introduction

Assuming that there is memory to spare, caching all, or part of Firefox's profile to RAM using tmpfs offers significant advantages. Even though opting for the partial route is an improvement by itself, the latter can make Firefox even more responsive compared to its stock configuration. Benefits include, among others:

  • reduced disk read/writes (ideal for SSD)
  • heightened responsive feel
  • many operations within Firefox, such as quick search and history queries, are nearly instantaneous

Both of previously mentioned options make use of native shared memory; /dev/shm, a directory that behaves just as ordinary mounted file systems do, only with the notable exception that all of its content is stored in RAM.

Because data placed therein cannot survive a shutdown, a script used when moving the whole profile to RAM overcomes this limitation by syncing back to disk prior system shut down, whereas only relocating the cache is a quick, less inclusive solution.

Method 1: Use PKG from the AUR

Relocate the browser profile to tmpfs filesystem, including /tmp for improvements in application response as the the entire profile is now stored in RAM. Another benefit is a reduction in disk read and write operations, of which SSDs benefit the most.

Use an active management script for maximal reliability and ease of use. Several are available from the AUR.

Refer to the Profile-sync-daemon wiki article for additional info on it.

Method 2: Build you own system

Relocating only the cache to RAM

Adapted from this forum post

After entering about:config into the address bar, create a new string by right-clicking in the bottom half, selecting New, followed by String. Assign its value:

browser.cache.disk.parent_directory

Now, double-click the newly created string and direct it towards the RAM directory:

/dev/shm/firefox-cache

Upon restarting Firefox, it will start using /dev/shm/firefox-cache as the cache directory. Do mind that the directory and its contents will not be saved after a reboot using this method.

Relocating the entire profile to RAM

Before you start

Before potentially compromising Firefox's profile, be sure to make a backup for quick restoration. Replace xyz.default as appropriate and use tar to make a backup:

$ tar zcvfp ~/firefox_profile_backup.tar.gz ~/.mozilla/firefox/xyz.default

The script

Adapted from verot.net's Speed up Firefox with tmpfs

The script will first move Firefox's profile to a new static location, make a sub-directory in /dev/shm, softlink to it and later populate it with the contents of the profile. As before, replace the bold sections to suit. The only value that absolutely needs to be altered is, again, xyz.default.

Be sure that rsync is installed and save the script to ~/bin/firefox-sync, for example:

firefox-sync
#!/bin/sh

static=main
link=xyz.default
volatile=/dev/shm/firefox-$USER


IFS=
set -efu

cd ~/.mozilla/firefox

if [ ! -r $volatile ]; then
	mkdir -m0700 $volatile
fi

if [ "$(readlink $link)" != "$volatile" ]; then
	mv $link $static
	ln -s $volatile $link
fi

if [ -e $link/.unpacked ]; then
	rsync -av --delete --exclude .unpacked ./$link/ ./$static/
else
	rsync -av ./$static/ ./$link/
	touch $link/.unpacked
fi

Close Firefox, make the script executable and test it:

$ killall firefox firefox-bin
$ chmod +x ~/bin/firefox-sync
$ ~/bin/firefox-sync

Run Firefox again to gauge the results. The second time the script runs, it will then preserve the RAM profile by copying it back to disk.

Automation

Seeing that forgetting to sync the profile can lead to disastrous results, automating the process seems like a logical course of action.

cron job

Manipulate the user's cron table using crontab:

$ crontab -e

Add a line to start the script every 30 minutes,

*/30 * * * * ~/bin/firefox-sync

or add the following to do so every 2 hours:

0 */2 * * * ~/bin/firefox-sync

Sync at login/logout

Deeming bash is being used, add the script to the login/logout files:

$ echo '~/bin/firefox-sync' | tee -a ~/.bash_logout ~/.bash_login >/dev/null
Note: You may wish to use ~/.bash_profile instead of ~/.bash_login as bash will only read the first of these if both exist and are readable.

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