1706383 - Investigate whether dom.ipc.processPriorityManager.backgroundGracePeriodMS may help with content terminations

Status: RESOLVED FIXED

(GeckoView :: General, enhancement, P1)

Description

[(No longer employed by Mozilla) Aaron Klotz]

This pref, as well as dom.ipc.processPriorityManager.backgroundPerceivableGracePeriodMS, cause the priority manager to wait until the grace period elapses before dropping priority.

Comment 1

[(No longer employed by Mozilla) Aaron Klotz]

Attachment: Bug 1706383: Set process priority manager grace periods for GeckoView Nightly; r=#geckoview-reviewers

Because of the way the process priority manager works, a tab switch may alter
priorities like so:

1. User switches from tab1 to tab2;
2. We drop tab1's content process priority;
3. We raise tab2's content process priority;

But if tab1 and tab2 live in the same content process, then not only is
the priority adjustment redundant, it gives Android an opportunity to kill
the content process between steps (2) and (3)!

By setting a brief grace period, the priority manager will wait a bit until
dropping priority of tab1:

1. User switches from tab1 to tab2;
2. We start the grace period for dropping tab1's priority;
3. We go to raise tab2's priority, but since the content process is already
   foreground, this becomes a no-op;
4. Grace period expires for tab1, but we see that tab2 is still using our
   content process, so the "drop" becomes a no-op.

Nightly only for now, we'll see how this affects tab kills.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/9927b4e6d1c1
Set process priority manager grace periods for GeckoView Nightly; r=geckoview-reviewers,agi

Comment 3

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/9927b4e6d1c1

Comment 4

[(No longer employed by Mozilla) Aaron Klotz]

I'm going to resolve this and follow up on the analysis elsewhere.