1667868 - Interacting with specific element of the PDSP Ki database search form freezes Firefox

Status: RESOLVED FIXED

(Firefox :: Untriaged, defect)

Description

[aerkiaga3]

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:81.0) Gecko/20100101 Firefox/81.0

Steps to reproduce:

1. Go to https://pdsp.unc.edu/databases/pdsp.php
2. Check 'Test Ligand'
3. Click the dropdown button at the right of that field

Actual results:

Firefox freezes after a few seconds, the 'MainThread' process at a constant 1 full core CPU usage.

Expected results:

After a quite noticeable but short time interval, a very long dropdown list should have appeared, listing all test ligands for which data exists in the database.

Comment 1

[aerkiaga3]

The User Agent listed above corresponds to the browser version and operating system this bug was successfully reproduced on.

Comment 2

[Pascal Chevrel:pascalc]

Confirmed with Nightly 83 on Linux.

Comment 3

[Paul Adenot (:padenot)]

https://share.firefox.dev/2S7iYGi hopefully shows the problem.

Emilio, want to have a look? This is spinning in https://searchfox.org/mozilla-central/source/toolkit/actors/SelectChild.jsm#379.

Comment 4

[Florian Quèze [:florian]]

(In reply to Paul Adenot (:padenot) from comment #3)

https://share.firefox.dev/2S7iYGi hopefully shows the problem.

Emilio, want to have a look? This is spinning in https://searchfox.org/mozilla-central/source/toolkit/actors/SelectChild.jsm#379.

Thanks for the profile! I think the issue is rather in the parent process: https://share.firefox.dev/3n3ZIbh

Comment 5

[Emilio Cobos Álvarez [:emilio]]

Both could be improved. I can look.

Comment 6

[Emilio Cobos Álvarez [:emilio]]

Attachment: Bug 1667868 - Optimize slotting for appends to a shadow host. r=smaug

Comment 7

[Emilio Cobos Álvarez [:emilio]]

Attachment: Bug 1667868 - Optimize directionality change handling during slotting. r=smaug

Same idea, when only one node is slotted or unslotted, we only need to
do work for the rest of assigned nodes iff the slot has dir=auto or a
dir=auto ancestor, and the result of computing the dir=auto ancestor
changes.

Otherwise we just need to propagate the directionality from the slot.

Depends on D91753

Comment 8

[Emilio Cobos Álvarez [:emilio]]

Well looking a bit closer, the improvements in the child process are probably a bit minor (micro-optimizing font-family serialization and so on), so probably worth doing in a separate bug.

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/62a557bcdc10
Optimize slotting for appends to a shadow host. r=smaug
https://hg.mozilla.org/integration/autoland/rev/d062c1f7777b
Optimize directionality change handling during slotting. r=smaug

Comment 10

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/62a557bcdc10
https://hg.mozilla.org/mozilla-central/rev/d062c1f7777b

Comment 11

[Florian Quèze [:florian]]

It would be nice to see a profile of the same thing with a build including the patches that have landed.

Comment 12

[Pascal Chevrel:pascalc]

Here is a profile after the patch, it's significantly improved but it is still slow for me https://share.firefox.dev/3l6zJ0P

Comment 13

[Florian Quèze [:florian]]

(In reply to Pascal Chevrel:pascalc from comment #12)

Here is a profile after the patch, it's significantly improved but it is still slow for me https://share.firefox.dev/3l6zJ0P

Thanks Pascal!

Emilio, is there anything in this profile that's actionable and would be worth a follow-up bug?

Comment 14

[Emilio Cobos Álvarez [:emilio]]

Yes, I think there are multiple things that could be improved:

• Half of the parent process time is running JS (custom element constructors, etc) which probably could do less work.
• Almost other half (60% of the remaining layout time) comes from nsTextBoxFrame::DoXULLayout... Chances are than moving this to something that isn't XUL would massively speed it up, it's not like there's so much text there...

So yeah, let's file a follow-up bug IMO.