1139918 - Gecko is doing layer transactions at 50fps when idle in the gallery app

Status: RESOLVED DUPLICATE of bug 962594

(Firefox OS Graveyard :: Performance, defect)

Description

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

Attachment: GDB backtrace

STR:
1. Turn on layer dumping from the developer menu
2. Enter the gallery app and wait for stuff to stop moving on the screen.

ER:
adb logcat output is quiet

AR:
adb logcat shows a continual flow of layer dumps, indicating new layer transactions arriving in the compositor.

I used the WebIDE devtools to try to see if it was some script running but as far as I can tell JS is idle and this is a gecko issue. I'm not 100% confident in the devtools performance pane so I can't say that for sure. But this is a pretty serious issue as it uses the CPU even when it's supposed to be idle and will cause battery drain if you're in the gallery app, whether on the image thumbnail view or viewing a specific image.

I have reproduced this on master builds on both Flame and Nexus 4. I grabbed a profile from a Flame, it is at [1], but it doesn't indicate what is causing the spin. A gdb backtrace of the child process of a random ctrl-c is also attached, and might shed some light.

[1] http://people.mozilla.org/~bgirard/cleopatra/#report=992823cebcc9909bde4c10a512795cab59710d50&selection=0,38,12

Comment 1

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

Turning on the nglayout.debug.invalidation pref just outputs this endlessly:

03-05 10:14:03.116 I/Gecko   (20739): Starting ProcessPendingUpdates
03-05 10:14:03.116 I/Gecko   (20739): ---- PAINT START ----PresShell(0xb24ca700), nsView(0xb24d4b70), nsIWidget(0xb2b196c0)
03-05 10:14:03.116 I/Gecko   (20739): ---- PAINT END ----
03-05 10:14:03.116 I/Gecko   (20739): Ending ProcessPendingUpdates
03-05 10:14:03.126 I/Gecko   (20739): Starting ProcessPendingUpdates
03-05 10:14:03.126 I/Gecko   (20739): ---- PAINT START ----PresShell(0xb24ca700), nsView(0xb24d4b70), nsIWidget(0xb2b196c0)
03-05 10:14:03.126 I/Gecko   (20739): ---- PAINT END ----
03-05 10:14:03.126 I/Gecko   (20739): Ending ProcessPendingUpdates

which indicates that nothing is actually getting painted. This agrees with the paintflashing results, which also indicate nothing getting repainted.

Comment 2

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

I tracked it down to a CSS animation on a <progress> element in the gallery app. Using WebIDE I see that the element in question has the style at [1] applied, but it's also display:none so we shouldn't be animating it in gecko.

[1] https://github.com/mozilla-b2g/gaia/blob/5ff50e269bb7ca49bb24decdb437b8ca8afcb911/shared/style/progress_activity.css#L8

Comment 3

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

qawanted for branch checks.

Comment 4

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

Never mind, this is a dupe of bug 962594.