When loading the following paper:
The performance is atrocious for a while. There's clearly an element of deferred loading impacting the performance, but in chrome the page starts scrolling after quite a delay, and then scrolls smoothly. In Safari, the scrolling remains extremely laggy, and fails to update. Per the inspector we're spending a lot of time in layout and rendering rather than js.
Created attachment 369230 [details]
Looks to be spending a tonne of time in/under/around
CA::CG::draw_glyph_bitmaps(CA::CG::Renderer&, CA::CG::FillGlyphs const&, CA::CG::ShadowStyle const*, bool, bool)
Instruments really should develop an understanding of dispatch queues.
The page seems to be very painting-heavy early on, then at some point get into a good state where it scrolls OK. Maybe rendering the pages lower down is triggering continual full repaints of the pages at the top.