964224 - [Tarako] Homescreen is relaunched in background in launching an app

Status: RESOLVED WONTFIX

(Firefox OS Graveyard :: Gaia::System::Window Mgmt, defect)

Description

[Cervantes Yu [:cyu] [:cervantes]]

On tarako, we observed that the homescreen is relaunched in background when we start an app and the homescreen is killed by the lowmem killer. This excessive launch of the homescreen increases app launch time.

JS stack of the excessive homescreen launch:
0 hw_render() [\"app://system.gaiamobile.org/js/homescreen_window.js\":46]
1 hw_ensure() [\"app://system.gaiamobile.org/js/homescreen_window.js\":169]
2 hl_getHomescreen() [\"app://system.gaiamobile.org/js/homescreen_launcher.js\":82]
3 windowOpened() [\"app://system.gaiamobile.org/js/window_manager.js\":273]
4 anonymous() [\"app://system.gaiamobile.org/js/window_manager.js\":193]
5 onloaded() [\"app://system.gaiamobile.org/js/window_manager.js\":208]

Comment 1

[(inactive after 6/18) Alive Kuo [:alive]]

This is a v1.3 only window mgmt. bug.
In v1.3 window manager, loadend of active app would trigger windowOpened() callback which brings homescreen to background.
But if homescreen dies before the app is loaded, we will mistakenly revive homescreen via HomescreenLauncher when we tried to send it to background.

Comment 2

[(inactive after 6/18) Alive Kuo [:alive]]

Attachment: https://github.com/mozilla-b2g/gaia/pull/15722

Prevent homescreen being revived at background.

Comment 3

[Cervantes Yu [:cyu] [:cervantes]]

Comment on attachment 8365894 [details] [review]
https://github.com/mozilla-b2g/gaia/pull/15722

Looks good on my Tarako.

Comment 4

[James Ho]

do we still need this? If yes, please finish it.

Comment 5

[Naoki Hirata :nhirata (please use needinfo instead of cc)]

Do we still need this patch?

Comment 6

[(inactive after 6/18) Alive Kuo [:alive]]

The patch here is unnecessary for some gecko fix is landed for tarako. Cerventus could you close this?

Comment 7

[(inactive after 6/18) Alive Kuo [:alive]]

Comment on attachment 8365894 [details] [review]
https://github.com/mozilla-b2g/gaia/pull/15722

Let's still get this reviewed for v1.3

Comment 8

[(inactive after 6/18) Alive Kuo [:alive]]

qawanted for v1.3T

Comment 9

[Naoki Hirata :nhirata (please use needinfo instead of cc)]

Alive, do you want us to test the patch on 1.3T?  
Just verifying what is being asked for qawanted, because the reason why it was flagged isn't clear.

Comment 10

[(inactive after 6/18) Alive Kuo [:alive]]

Sorry, I want to know if this still happens on 1.3T before the patch is applied.

Comment 11

[(inactive after 6/18) Alive Kuo [:alive]]

Comment on attachment 8365894 [details] [review]
https://github.com/mozilla-b2g/gaia/pull/15722

This patch is low rick but changes timing to send homescreen to background.
We may not have problem here on a not-low-end problem because homescreen won't be killed oftenly, but in low end device like tarako the timing is the king.

NOTE: Please see https://wiki.mozilla.org/Release_Management/B2G_Landing to better understand the B2G approval process and landings.

[Approval Request Comment]
[Bug caused by] (feature/regressing bug #):
[User impact] if declined:
[Testing completed]:
[Risk to taking this patch] (and alternatives if risky):
[String changes made]:

Comment 12

[Cervantes Yu [:cyu] [:cervantes]]

I can confirm that this bug is still present on 1.3t. We had many tuning of OOM parameters so we might not see homescreen killed during startup of other apps, but if I manually kill homescreen during app launch, I still see it relaunched.

Comment 13

[Naoki Hirata :nhirata (please use needinfo instead of cc)]

removing qawanted based on comment 12

Comment 14

[bhavana bajaj [:bajaj]]

Hey :alive,

Since this does not impact non-low end phones and really needed for tarako, no need to land on 1.3 branch.Hence minusing the approval request here.

TO get this landed on tarako,

 Nominate this for 1.3t:? while parallel landing this patch on master..Once this blocked on 1.3T+, we would have to cherry pick get this landed on 1.3T branch and v1.4.

Comment 15

[Naoki Hirata :nhirata (please use needinfo instead of cc)]

root@android:/ # b2g-ps
APPLICATION      USER     PID   PPID  VSIZE  RSS     WCHAN    PC         NAME
b2g              root      408   1     65112  12504 ffffffff 400d1dec S /system/b2g/b2g

I'm not sure exactly how I got to this state as of yet.
If I figure it out I will report another bug.  I think having no homescreen is worse than slow performance due to the homescreen relaunching at the same time as another app...

Comment 16

[BMO Automation]

Firefox OS is not being worked on