User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:94.0) Gecko/20100101 Firefox/94.0

Steps to reproduce:

Navigate through my bookmarks folders using the bookmarks toolbar.

Actual results:

Firefox quickly uses hundreds of MBs. This memory is per window, meaning that navigating through bookmarks in multiple windows can use GBs of memory. Some of the memory is released when you click the Minimize Memory button in about:memory, but most of it is only released when you close the window, for example by moving all of its tabs in a new window.

Expected results:

This was introduced when the Software WebRender started being used in the popup menus. The memory accumulates in explicit > gfx > webrender > swgl (it's not more detailed than that, so there's no point in uploading a full memory report). Setting gfx.webrender.software.unaccelerated-widget.allow to false, when it was available (it's still is in the stable version), worked around the issue.

Moving to gfx-triage.

Gfx Triage Notes:
This should be solved with https://bugzilla.mozilla.org/show_bug.cgi?id=1654938, ideally. There are no easy solutions.