Comment 39 for bug 1959747

(In reply to Sören Hentzschel from comment #31)
> > which has removed the possibility of disabling webrender
>
> I assume you already tried the newest graphics drivers.
>
> Why would you want to *completely * disable WebRender? Do hardware AND software WebRender crash for you? You can set gfx.webrender.software to true to disable hardware WebRender and enable software WebRender instead. Please try this instead of using an e-mail client with security vulnerabities (since Thunderbird 91 won't receive any further security update we have to assume that Thunderbird 91 is insecure now).

Perhaps it's not actually realted to webrender, I just assumed that because disabling it solved problems in the past. I use the drivers built into the kernel and I am on a 5.18 kernel. There were no differences in performance with software mode, so it could very well not be related to webrender.

It seems that the high CPU usage and slow UI update is worse when the message list is big and the window is big. If I make it that only 10 rows are visible, it seems to be faster. Here is a profile of the mouse moving around a large message list. https://share.firefox.dev/3y3PfU2