My Firefox has been very slow, using almost 5GB of memory and 100% of CPU for the last couple hours. I've noticed that I had accidentally left in the background a browser console window. about:memory shows: 4,837.68 MB (100.0%) -- explicit ├──2,315.89 MB (47.87%) ── heap-unclassified ├────824.87 MB (17.05%) -- heap-overhead ... ├────781.28 MB (16.15%) -- js-non-window │ ├──679.33 MB (14.04%) -- zones │ │ ├──616.00 MB (12.73%) -- zone(0x11a550000) │ │ │ ├──266.00 MB (05.50%) ── unused-gc-things │ │ │ ├──201.19 MB (04.16%) -- compartment([System Principal], Addon-SDK (from: resource://gre/modules/commonjs/toolkit/loader.js:249)) │ │ │ │ ├──174.06 MB (03.60%) -- classes │ │ │ │ │ ├───90.40 MB (01.87%) -- class(Object)/objects ... ├────639.51 MB (13.22%) -- window-objects │ ├──316.15 MB (06.54%) -- top(none) │ │ ├──305.65 MB (06.32%) -- detached │ │ │ ├──270.80 MB (05.60%) -- window(chrome://devtools/content/webconsole/webconsole.xul) │ │ │ │ ├──232.83 MB (04.81%) -- dom │ │ │ │ │ ├──232.69 MB (04.81%) ── orphan-nodes Anonymized report attached. I'm not exactly sure of what happened, but I think I left the console open for at least 2 days. Closing it doesn't seem to free memory. I have gmail open in an app tab, and I suspect it causes a lot of output to go continuously to the console.

After clicking the 'Minimize memory usage' button, the webconsole.xul window disappears from the report, which now starts with: 3,822.36 MB (100.0%) -- explicit ├──1,991.01 MB (52.09%) ── heap-unclassified ├──1,011.04 MB (26.45%) -- heap-overhead

I think this might be a duplicate of bug 1197789. I don't think this only happens with the console, I've reproduced it with the inspector too. And in my experience, you only need to open a panel once, and the memory leak starts, closing it doesn't stop the leak.

I'm marking the other bug as a blocker for this. Once there's a fix for that, we can see if this is fixed.

Can you still reproduce this, Florian?

I still have excessive memory usage. about:memory starts with: 5,448.93 MB (100.0%) -- explicit ├──2,606.90 MB (47.84%) ── heap-unclassified And I still believe having used the console at some point before is related.