825483 - Reduce bfcache size on low memory devices

Status: RESOLVED FIXED

(Firefox for Android Graveyard :: General, defect)

Description

[Wesley Johnston (:wesj)]

We currently hardcode our bfcache to 1 page (for each tab I think?) [1]. We could lower it on low memory devices. The dynamic calculation in Firefox guesses about 4MB per entry [2], so it could be a 4MB per tab win. Alternatively, we could fix the dynamic calculation to be a bit more conservative and turn it on everywhere.

[1] http://mxr.mozilla.org/mozilla-central/source/mobile/android/app/mobile.js#109
[2] http://mxr.mozilla.org/mozilla-central/source/docshell/shistory/src/nsSHistory.cpp#272

Comment 1

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

I'd like to better understand the difference between "max_entries" and "max_total_viewers". Reducing "max_total_viewers" means setting it to zero, which means turning it off. How does that affect bfcache? Would reducing "max_entries" be a simpler change that does not completely turn off bfcache? How much memory is reduced by changing "max_entries" ?

Comment 2

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

Can we get someone to make some settings changes, then run about:memory (or dump it using the intent) to compare the differences? If we can see some noticeable wins, these would be easy preferences to adjust dynamically in response to memory limits.

Wesj - Maybe ckitching would be able to do this?

Comment 3

[Wesley Johnston (:wesj)]

Argh. Forgot this. If a volunteer wants to look at about:memory a bit, I'd be happy to help you.

Comment 4

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

Updating the links a bit:

The auto-calculate code where the 4MB estimate is shown:
http://hg.mozilla.org/mozilla-central/diff/9b2a99adc05e/docshell/shistory/src/nsSHistory.cpp

We already have code to evict all content viewers on a memory-pressure:
http://hg.mozilla.org/mozilla-central/diff/051b3d8ed545/docshell/shistory/src/nsSHistory.cpp

Let's use this bug to just set the pref to 0 for low memory devices, so they have less chances of OOMs.

Comment 5

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

Attachment: no-bfcache-on-lowmemory v0.1

Simple fix adds a session-default pref on low memory trigger.

Comment 6

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

https://hg.mozilla.org/integration/fx-team/rev/983c6b50a431

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/983c6b50a431