999161 - Random switching of fonts during Kraken benchmark

Status: NEW

(Firefox :: General, defect)

Description

[Elbart]

Attachment: kraken.jpg

When doing the benchmark on Windows, the font of the test-panel is randomly switching from Times New Roman to Arial and back.

Easily reproducible on sufficiently fast machines right after a fresh boot.

Screenrecording: http://elbart.bplaced.net/bugzilla/kraken_font_switching.mp4


Regression range:
Last good revision: 0f7261e288f2 (2013-03-15)
First bad revision: 8f5b1f9f5804 (2013-03-16)
Pushlog:
http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=0f7261e288f2&tochange=8f5b1f9f5804

Comment 1

[Elbart]

Bisecting on m-i:
>$ hg bisect -g
>The first bad revision is:
>←[0;33mchangeset:   124821:d4a5a1e1e8e9←[0m
>user:        Avi Halachmi <[e-mail]>
>date:        Wed Feb 20 20:21:09 2013 +0200
>summary:     Bug 590422: Remove delay line filter from timer thread. r=bz

Comment 2

[[SV Manager] Florin Mezei, QA (:FlorinMezei)]

I can easily reproduce this on Windows 7 x64, with Nightly from 2013-03-16 (User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:22.0) Gecko/20130316 Firefox/22.0, BuildID: 20130316030854), each time I start the benchmark right after opening Firefox.

However, I can no longer reproduce this on the latest Firefox 33 Nightly (User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:33.0) Gecko/20100101 Firefox/33.0, BuildID: 20140625030206).

Elbart, can you confirm if this is working fine in the latest Firefox 33 Nighlty (ftp://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-mozilla-central/)?

Comment 3

[Elbart]

It's not happening as often as in older builds, but occasionally it is still happening for me, yes.

Comment 4

[Elbart]

I reran the Kraken-benchmark 1.1 on Nightly 2015-07-05, and now the font-switching is pretty much happening for every step of the benchmark.
This is way worse than it was a year ago.

Can you confirm this?

Comment 5

[[SV Manager] Florin Mezei, QA (:FlorinMezei)]

I've tried this today and indeed it's easily reproducible on Windows 7 x64 with:
- latest Firefox 42 Nightly - BuildID=20150705030216
- latest Firefox 41 Aurora - BuildID=20150706004011
- Firefox 40 Beta 1 - BuildID=20150702173756

Steps to reproduce:
1. Start Firefox (I used clean profiles).
2. Load http://krakenbenchmark.mozilla.org/ and click "Begin".

Expected results: 
While the benchmark is running the same font is used to display the tests (Times New Roman?).

Actual results:
While the benchmark is running the font is constantly switched between Times New Roman and Arial. The video in comment 0 describes the issue very well. 

Notes:
It seems to me that each time we get "Read krakenbenchmark.mozilla.org" on the bottom of the window, then we also switch the font on the page.

Comment 6

[Elbart]

I discovered that the increase of the occurrence of font-switching is because of e10s.
With e10s disabled, the font-switching is only happening approx. five times during a benchmark run, like before.

Another benchmark showing this is the older SunSpider 1.0.1.
https://www.webkit.org/perf/sunspider/versions.html