Tor Browser high CPU usage while browsing Facebook

Hi, Tor Browser with a single page open - facebook, after scrolling a little CPU usage jumps to more than 60% of my fast notebook CPU.

See stack details in attachment.

Reproducibility: 100%

Tor Browser 7.5.5 (based on Mozilla Firefox 52.8.1) (32-bit) Windows 10

Trac:
Username: uzi

added component::applications/tor browser owner::tbb-team priority::high reporter::uzi severity::major status::new type::defect labels

Trac:
Username: uzi

Trac:
Username: uzi

I'm also seeing high CPU usage on facebookCoreWWWi.onion (facebook's onion service), so much in fact that it started boiling my stomach from the cpu overheating... I have the latest HTTPS-E (with the fix), and on Linux...

Forgot to mention: not just on facebook, but on many other sites EVEN WITH THE SAFEST SECURITY SETTING which normally keeps the hungry JS in its cage.

The safest security setting turns off JavaScript, but it also turns off a lot of optimisations. (Because optimisations are fingerprintable.)

I'll leave it to the Tor Browser devs to analyse your stack trace.

Replying to teor:

The safest security setting turns off JavaScript, but it also turns off a lot of optimisations. (Because optimisations are fingerprintable.) Optimisations of JS (i.e. basically JIT) have nothing to do with that since JS itself is entirely blocked, so why am I getting 100% CPU usage in a simple forum on high security setting? (precision: while it's loading up, when the page finally loads up it becomes better)

On the bright side: a FF60-esr based Tor Browser alpha is coming out very soon which will likely not have such a bug. On the darker side: using it will make you more fingerprintable.

Replying to cypherpunks:

Replying to teor:

The safest security setting turns off JavaScript, but it also turns off a lot of optimisations. (Because optimisations are fingerprintable.) Optimisations of JS (i.e. basically JIT) have nothing to do with that since JS itself is entirely blocked, so why am I getting 100% CPU usage in a simple forum on high security setting? (precision: while it's loading up, when the page finally loads up it becomes better)

JavaScript isn't the only thing that browsers optimise.

Edit: Browsers optimise parts of the rendering pipelines as well.

moved to tpo/applications/tor-browser#26473 (closed)