803575 - [Native Fennec] Expire tabs based on LRU and age

Status: RESOLVED FIXED

(Firefox for Android Graveyard :: General, defect)

Description

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

We need to figure out if/when to turn on the tab expiration added in bug 792143. Some possible options:

1) Pref it on for all ARMv6 builds at compile-time
2) Pref it on for low-memory devices at run-time (assuming bug 801818 is fixed)
3) Wait until we hit a low-memory situation at runtime and then turn it on
4) Some combination of the above
5) Other?

Comment 1

[Brad Lassey [:blassey] (use needinfo?)]

my preference would be for #3. I think taras would prefer having it on all the time (for battery consumption rather than memory), CC'ing him.

Comment 2

[(dormant account)]

(In reply to Brad Lassey [:blassey] from comment #1)
> my preference would be for #3. I think taras would prefer having it on all
> the time (for battery consumption rather than memory), CC'ing him.

I think #3 is a good start, can investigate more aggressive approaches once #3 lands.

Comment 3

[Mark Finkle (:mfinkle) (use needinfo?)]

Agreed that #3 is a good start. It would be nice if we could make this a session-only pref. I mean, each time we'd start a new Firefox, we'd start _not_ expiring tabs. We could do that by setting the "default branch" version of the preference:

let defaults = Services.prefs.getDefaultBranch();
defaults.setIntPref(...);

Such a pref value is only retained while Firefox is running and is reset to the real default value upon restart.

Food for thought.

Comment 4

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

Was discussing this with Brad today, and I want to clarify the existing behaviour and exactly what this bug is for.

Currently:
1) we unconditionally zombify all background tabs when we get a memory-pressure event (this was added in bug 784040)
2) time-based tab zombification (added in bug 792143) is completely disabled

"Time-based tab zombification", if enabled, will trigger zombification of a zero or one tabs when a new tab is opened. The tab that is zombified is the least-recently-used tab, if and only if the tab hasn't been used for browser.tabs.zombieTime seconds.

This bug is about when to enable "time-based tab zombification". My preference is to turn it on by default for low-memory devices, and to turn it on after receiving the first memory-pressure event on high-memory devices. I can add another boolean check or pref control exactly when the behaviour is enabled, if needed (or I could try to do it using the "default branch" of the pref as mark suggested).

Comment 5

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

Attachment: Patch

This patch (1) assumes that my patch from bug 801818 is in the tree and (2) calls the new behaviour "pre-emptive zombies" because i suck at coming up with good names for things. Suggestions welcome, but I'll wait on requesting review until bug 801818 is actually landed.

Comment 6

[Mark Finkle (:mfinkle) (use needinfo?)]

You could refer to this action as "tab expiration" (you filed it that way) and use:
Tabs._enablePreemptiveZombies -> Tabs._enableExpiration
browser.tabs.zombieTime -> browser.tabs.expirationTime

I'm fine with zombies too, so up to you :)

Comment 7

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

Attachment: Patch (v2)

Comment 8

[Mark Finkle (:mfinkle) (use needinfo?)]

Comment on attachment 677088 [details] [diff] [review]
Patch (v2)

Looks like a good start. Would telemetry probes for expiring tabs be useful to help us see how often the code is executing?

Comment 9

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

(In reply to Mark Finkle (:mfinkle) from comment #8)
> Looks like a good start. Would telemetry probes for expiring tabs be useful
> to help us see how often the code is executing?

Good call, I've filed bug 808003 as a follow-up for that.

Comment 10

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

https://hg.mozilla.org/integration/mozilla-inbound/rev/5981344041a1

Comment 11

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/5981344041a1