Firefox: Turning off JIT makes it faster?

mindfall · 2009-07-16 20:27:32

With respect to the recently found vulnerability I decided to turn off Firefox's dynamic JS compiler, and suddenly Firefox feels a lot faster and snappier to me. Weird.

So, In about:config/*jit*, what does False actually mean? Does it mean "JIT off" or rather "JIT not off" (I switched it to False)?
How do I find out it it's on or off?

Last edited by mindfall (2009-07-16 20:28:19)

cactus · 2009-07-16 20:49:38

false means the JIT is turned off.
firefox 'feels' a bit slower for me, but not too bad. However, I noticed that the cpu usage on JS heavy sites is quite a bit higher, and firefox seems to 'pause' once in a while on such sites.

Last edited by cactus (2009-07-16 20:50:41)

Wintervenom · 2009-07-16 20:50:25

If it is true, then it is on, and vise-versa. And it looks like Cactus beat me to the punch.

Last edited by Wintervenom (2009-07-16 20:51:00)

cactus · 2009-07-16 20:56:55

the punch was good, like koolaid with some vodka thrown in.

mindfall · 2009-07-17 00:45:14

Thanks, I guess false==!off would have really been stupidly counterintuitive
Anyway, it's weird. I ran Sunspider benchmark and with JIT on it would - as expected - be ~2.5 times faster.
Yet still I get those little delays and micro-freezes when browsing, making it feel faster without JIT

pauldonnelly · 2009-07-17 20:32:29

That's not surprising. Interpreting code is faster than compiling it. Without the compiler, the browser can launch into running the code right away. If it compiles it first, that means a lag. Of course, if you run the same section of code over and over the compilation cost is absorbed by the decreased run time. You'd hope that the JIT only took the time to compile things that needed it... but maybe it doesn't. Or maybe it does. But there are reasons that it could introduce a lag at times. Haven't noticed any lag myself.

Last edited by pauldonnelly (2009-07-17 20:33:45)

R00KIE · 2009-07-18 21:21:13

Some pages are .... well too overloaded with stuff that doesn't matter just to make them look a bit shinny. I guess it is a problem of how things are done with firefox that makes it slow down but firefox is worthless without web pages so ... I would say firefox isn't the only one to blame.

Arch Linux

#1 2009-07-16 20:27:32

Firefox: Turning off JIT makes it faster?

#2 2009-07-16 20:49:38

Re: Firefox: Turning off JIT makes it faster?

#3 2009-07-16 20:50:25

Re: Firefox: Turning off JIT makes it faster?

#4 2009-07-16 20:56:55

Re: Firefox: Turning off JIT makes it faster?

#5 2009-07-17 00:45:14

Re: Firefox: Turning off JIT makes it faster?

#6 2009-07-17 20:32:29

Re: Firefox: Turning off JIT makes it faster?

#7 2009-07-18 21:21:13

Re: Firefox: Turning off JIT makes it faster?

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