1714926 - 10.28 - 7.79% about_newtab_with_snippets / about_newtab_with_snippets (Linux) regression on Wed June 2 2021

Status: RESOLVED WONTFIX

(Core :: Graphics: WebRender, defect)

Description

[Florin Strugariu [:Bebe]]

Perfherder has detected a talos performance regression from push 1bd8392043898ae63e8669d6ffd8bf4fa64b699e. As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
10%	about_newtab_with_snippets (docs)		linux1804-64-shippable-qr	e10s stylo webrender-sw	41.86 -> 46.17
8%	about_newtab_with_snippets (docs)		linux1804-64-shippable-qr	e10s stylo webrender-sw	42.25 -> 45.54

Improvements:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
8%	tscrollx (docs)		linux1804-64-shippable-qr	e10s stylo webrender-sw	1.26 -> 1.17
7%	displaylist_mutate (docs)		linux1804-64-shippable-qr	e10s stylo webrender-sw	2,484.41 -> 2,302.41
6%	displaylist_mutate (docs)		macosx1015-64-shippable-qr	e10s stylo webrender-sw	2,106.59 -> 1,972.93

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests. Please follow our guide to handling regression bugs and let us know your plans within 3 business days, or the offending patch(es) will be backed out in accordance with our regression policy.

For more information on performance sheriffing please see our FAQ.

Comment 1

[Nicolas Silva [:nical]]

Ok this is going to be a bit complicated. The patches I landed change the way we store rectangles in the graphics code from one representation (origin+size) to another (top-left+bottom-right) that is more adapted to what we do, motivated by performance among other things. Because we have a lot of rectangle manipulation it would be too hard to change all rectangles in WebRender at once so I'm going incrementally. This introduces a lot of back and forth which may cause some inefficiencies, but the goal is to eventually move everything over to the same representation so that overhead will go away over time. There's going to be a lot of churn there as it's a long a tedious process so we'll have to take the hits while it's happening (fortunately here it's more a trade than just regressions).