1256133 - Slow, janky scrolling on this support.mozilla.org thread with e10s enabled

Status: RESOLVED WORKSFORME

(Core :: Panning and Zooming, defect, P3)

Description

[Nickolay_Ponomarev]

On a new profile, current nightly:
1. Open https://support.mozilla.org/en-US/questions/1111080
2. Scroll to the bottom of the page with Cmd+Down or with the three(?)-finger swipe.
3. Scroll to the top
4. Repeat

With e10s scrolling is much slower.

When taking the profiles below I did this: scroll down, scroll up, wait a second; repeat.

e10s: https://cleopatra.io/#report=fd056b554af26623e0d24467e351a89d799664e5&filter=%5B%7B%22type%22%3A%22RangeSampleFilter%22,%22start%22%3A214795,%22end%22%3A217711%7D,%7B%22type%22%3A%22RangeSampleFilter%22,%22start%22%3A216117,%22end%22%3A216767%7D%5D&selection=0,2662,2663,2664,2665,2359,2666,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,1039,1040,1041,1042,1043,1044,2713,2714,2715,2716,168,169,170,171,183,184,185,186,187,188,189,190,214,215,216,217,218,219,2877,2878,2879,196,197,198,199,2889

no e10s: https://cleopatra.io/#report=f0ac7ed640459a01ac92b87533ab7f23eb1ae32d&filter=%5B%7B%22type%22%3A%22RangeSampleFilter%22,%22start%22%3A15676,%22end%22%3A17733%7D%5D&selection=0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,502,503,504,505,506,507,508,509,510,511,1758,343,344,447,448,449,450,451,453,463,464,465,466,467,468,468,469,470,738,739,740,472,473,474,475

This is likely a duplicate, but I couldn't find a list of known root causes of bad scrolling perf, and a way to confirm that my problem matches a known cause, so I'm filing this anyway.

Comment 1

[Jeff Muizelaar [:jrmuizel]]

What do you mean by slow scrolling? Is it jumpy or is there missing content?

I expect this might have to do with the horizontal scrolling. Do you see this problem on other support questions that are not horizontally scrollable?

Comment 2

[Jeff Muizelaar [:jrmuizel]]

Is this on a retina screen?

Comment 3

[Nickolay_Ponomarev]

The scrolling is jumpy: you can notice the time it takes to paint the next frame, both visually and in the profile.

This is a retina screen, yes.

> I expect this might have to do with the horizontal scrolling. 
That was a good guess! I removed the wide <p> from the first post (using the Devtools Inspector) and scrolling became as fast as without e10s.

Comment 4

[Botond Ballo [:botond]]

Bug 1251638 is another bug where we've seen the presence of a horizontally scrollable element have a negative effect on scrolling performance. It's possible these share a root cause.

Comment 5

[Jim Mathies [:jimm]]

kats, apz related?

Comment 6

[Kartikaya Gupta (email:[e-mail])]

Yeah this is next on my to-do list.

Comment 7

[Kartikaya Gupta (email:[e-mail])]

I've been using bug 1243081 to investigate since I'm assuming they're the same underlying issue, and it's easier for me to reproduce on that URL. From the APZ side I don't think there's much we can do here without making checkerboarding worse. Doing something like implementing bug 1261166 might help.

Comment 8

[Kartikaya Gupta (email:[e-mail])]

As with bug 1243081, applying the WIP patch on bug 1261166 makes the transaction times here drop to ~0. I specifically tested scrolling up and down on the provided URL using fn+left/right arrow (equivalent to "home"/"end" scrolling on mac) and compared the transaction times with and without bug 1261166.

Comment 9

[Botond Ballo [:botond]]

(In reply to (Back on May31) Kartikaya Gupta (email:[e-mail]) from comment #8)
> As with bug 1243081, applying the WIP patch on bug 1261166 makes the
> transaction times here drop to ~0.

Just to make sure I'm understanding this correctly: the slowness here is specific to Mac?

Comment 10

[Kartikaya Gupta (email:[e-mail])]

I believe so.

Comment 11

[Kartikaya Gupta (email:[e-mail])]

Unassigning since I'm not doing anything here, it is just waiting on the ClientStorage implementation.

Comment 12

[Kartikaya Gupta (email:[e-mail])]

Sounds like the ClientStorage work is still stalled, so this won't get fixed for 49 or 50 most likely.

Comment 13

[Sylvestre Ledru [:Sylvestre]]

Moving to p3 because no activity for at least 1 year(s).
See https://github.com/mozilla/bug-handling/blob/master/policy/triage-bugzilla.md#how-do-you-triage for more information