1289187 - Slow tab startup time with new content process

Status: RESOLVED FIXED

(Core :: DOM: Content Processes, defect, P3)

Description

[Jared Lockhart [:jlockhart]]

I am running Firefox Nightly 50.0a1 (2016-07-25) with dom.ipc.processCount set to a large number (100 in this case).  When I open a new tab, it starts a new content process and attaches it to the tab.  However this startup time introduces a noticeable lag to the new tab open flow.  

If I reduce the number of content processes so that it is equal to or lower than the number of tabs I have open, such that opening a new tab will reuse an existing content process, then the new tab open flow is extremely smooth. Is it possible to improve the performance of opening a new tab and starting a new content process, possibly by pre-creating a dormant background content process which is then brought to the front when a new tab is created?

Comment 1

[Lily Kim]

Yup, there is a really noticeable slowdown, but the advantages for me so far outweigh that. 

The pre-creating a dormant sounds great for a new tab, but I am wondering how handling of several new tabs would work. 

I frequently open something like 10+ tabs at the same time, but I am probably an edge case.

Comment 2

[Andrew Sutherland [:asuth] (he/him)]

There is preallocated process mechanism that seems like it works at least a little if you set the boolean pref "dom.ipc.processPrelaunch.enabled" to true.  You probably need to manually create it in about:config.  (Disclaimer: I think it's largely from Firefox OS, maybe there are scary things that break if you turn it on?  But it seemed to not explode too badly for me, and other than being intertwined with some "app" code paths, the code seems like it should work at least some of the time.)

Anyways, it's probably worth trying.

Comment 3

[Lily Kim]

Thanks for the heads up! I'll try to enable it and see how it goes.

Comment 4

[Lily Kim]

After having it on for a few days, it really does make loading up new tabs a lot better, just wish there was a preference for how many idle processes to pre-launch.

Comment 5

[Sylvestre Ledru [:Sylvestre]]

Moving to p3 because no activity for at least 1 year(s).
See https://github.com/mozilla/bug-handling/blob/master/policy/triage-bugzilla.md#how-do-you-triage for more information

Comment 6

[Chris Peterson [:cpeterson]]

Tracking for Fission MVP

Randell, is this "tab startup is slow" bug (from 2016) still useful? Is there a more recent Fission perf bug was can resolve this bug as a duplicate of?

Comment 7

[Randell Jesup [:jesup] (needinfo me)]

procesPreLaunch defaults to true nowadays (Bug 1385249 in 2017) for desktop, so this bug is moot now. I'll be filing bugs around expanding preallocated processes for fission and caching processes; they will be blockers to bug 1602010