1616421 - First page load is slower in Fenix when extensions are installed

Status: RESOLVED WORKSFORME

(GeckoView :: Extensions, defect, P1)

Description

[[ex-Mozilla] Agi Sferro | :agi]

Need to attach a profile, but I keep forgetting so I'm opening a bug at least.

:csadilek mentioned this to me and I've seen it too, the first pageload when ublock is enabled in Fenix is really slow, we should look at it and see what we can do about it.

Comment 1

[[ex-Mozilla] Agi Sferro | :agi]

Profiles:

No ublock: https://perfht.ml/2SZhjTf
With ublock: https://perfht.ml/2P5p6Ow

Comment 2

[[ex-Mozilla] Agi Sferro | :agi]

Looks like this is due uBlock using localStorage in the background script at startup time which causes us to wait synchronously for disk before performing the first network request.

Comment 3

[Markus Stange [:mstange]]

Can you add the IPDL Background thread to your list of profiled threads, and also enable the ipcmessages profiler feature? That might let us see what exactly is happening during that pause.

Comment 4

[Markus Stange [:mstange]]

Oh, also the DOM File thread which seems to be used here.

Comment 5

[[ex-Mozilla] Agi Sferro | :agi]

There you go! https://perfht.ml/2PblvOW

(let me know if there's anything else that can help there)

Comment 6

[[ex-Mozilla] Agi Sferro | :agi]

The performance fix has been resolved in uBlock 1.5.2, and I don't see any indication that we're actually slower than Fenix on this particular case, so I'm going to resolve this.