Thursday, March 12th 2009

Firefox 3.1 beta 3: Faster but Slower

A couple of days ago I tested how good the latest unreleased browsers from Opera, Microsoft, Mozilla, Apple and Google are at running Javascript.

Today Mozilla released Firefox 3.1 beta 3. So I gave it a spin on the Sunspider and V8 Javascript benchmarks.

I was obviously expecting it to do better than beta 2 in both tests, but that didn’t quite turn out to be the case. Below are averages from three runs of each combination of browser and benchmark, using a clean Firefox profile. (Not safe mode, since that will reduce Javascript speed in beta 3!)

Edit: I just added the data from my previous test for the non-Firefox browsers, for comparison. I also made a nice new graph.

To make the two benchmarks more comparable I’ve normalized the scores (inverting the time data from Sunspider, turning it into speed). The winner of each benchmark is given 100 and the others are given relative scores.

And here is the raw data (averages for three runs):

Browser	Sunspider (lower is better)	V8 (higher is better)
Firefox 3.1 b2	1,737ms	133
Firefox 3.1 b3	2,150ms	201
Opera 10 a	6,188ms	137
IE 8 rc1	7,994ms	47
Safari 4 b	1,633ms	1,056
Chrome 1.0	1,761ms	1,136

That’s pretty weird stuff. Beta 3 runs the V8 benchmark 51% faster than beta 2. But it chugs through the Sunspider benchmark 19% slower. (Or taking 24% longer, if you wish … 2150/1737 = 1.238 and 1/1.238 = 1-0.192)

Does anyone happen to know why this is the case? Was this a strategic move from the Firefox developers? I mean, did they introduce this slight performance regression knowingly, intending to fix it for final release?

Posted at 22:41. Tags: Mozilla. Categories: browsers, Mozilla Firefox. Both comments and trackbacks are closed.

One Response to this post:

1. Execvator says:

   March 15, 2009 at 19:20

   Whatever the cause, it seems to be mostly fixed now. Bug 481103 – TM: Dromaeo v3 Sunspider massive slowdown after 2-28 merge