I'm running the Ubuntu snap version of Firefox and recently I've had a problem where the more files I download the more sluggish downloads become. When I download a file now, even a few KB, Firefox becomes unresponsive for a few seconds, including video in other windows freezing. For longer downloads, Firefox is unresponsive the entire time. During downloads Firefox uses 1 core 100% in htop and about:performance shows "Firefox" using 100%
Clearing all data in settings doesn't help
Clearing the list of downloaded files doesn't help.
Deleting the profile fixes it, but the problem comes back as I download files.
I have a policies.json file that sets some privacy related settings and installs 3 addons (uBlock0@raymondhill.net, treestyletab@piro.sakura.ne.jp, @testpilot-containers).
I also have a hosts file that blocks all mozilla domains (except addons.mozilla.org)
I have a fast CPU, tons of ram and a nvme drive.
I'm not really sure how to debug this?
Since you're blocking Mozilla domains, my first thought was that it might have to do with the automatic malware checks for downloaded files. But the knowledge base article says it only checks executables, and it doesn't sound like it tries to contact a Mozilla server either.
But yeah, maybe you want to try turning that off in the settings for debugging either way.
The other suspicion is immediately Snap, primarily because I've seen quite some brokenness from Snap Firefox already.
You can try downloading the non-Snap version from the webpage directly: https://www.mozilla.org/en-GB/firefox/all/desktop-release/linux64/
That'll give you a
.tar.bz2, which you just unpack and run thefirefoxbinary inside.If it works there and you want to permanently switch, you probably want to use Mozilla's APT repo: https://support.mozilla.org/en-US/kb/install-firefox-linux#w_install-firefox-deb-package-for-debian-based-distributions-recommended
Getting the mozilla build fixed the issue, thanks.
How weird. A little unfortunate too since the snap version has apparmor confinement.