Comments on: Jiffy Firebug Plugin: Fine grained calculation of performance timings

By: Jaaap

Jaaap — Thu, 26 Jun 2008 14:27:53 +0000

This sucks.
Just to download, i had to create an account on addons.mozilla.org
Then after downloading it gave an error that the hash didn’t match.
Fine. Whatever.

By: billwscott

billwscott — Tue, 24 Jun 2008 15:45:58 +0000

The screen shot was mine (Bill Scott).

The Round Trip is something that I wrote internal to Netflix. You can see an example of it here: http://farm4.static.flickr.com/3256/2597183452_c3def20fcb_o.png. I plan on incorporating this visualization into the jiffy extension.

The Coder extension can be found here: http://getlivecoder.com/. It is basically a debugger for Firebug or Firefox Extensions. Lets you poke around in the chrome, modify js on the fly.

The jiffy extension is in the “experimental” sandbox area. Until it finishes the review process you have to login to get it unfortunately. Hopefully it can move out into the regular area. (all extensions go through this process)

By: sandrejev

sandrejev — Tue, 24 Jun 2008 12:23:11 +0000

Very nice though the results were sometime questionable. It’s always good when new developer tools appear.

By: GalloNero

GalloNero — Tue, 24 Jun 2008 08:36:36 +0000

Just to let others know. I had to register at Firefox Add-ons to download this plugin.

By: urandom

urandom — Tue, 24 Jun 2008 08:28:32 +0000

Just to continue Dashifen’s comment (since I don’t even know Firecookie), is there a repository for firebug-1.2 plugins?

By: Dashifen

Dashifen — Mon, 23 Jun 2008 21:36:17 +0000

I’ll have to play around with this a bit more. I installed it at work, added the jiffy.js script to my development site, and then checked it out and wasn’t getting much data, though I suspect that could be due to the fact that my sites are all cached already.

I have a different question for you though, Dion: what are the “Round Trip” and “Coder” tabs in your Firebug display? The others (YSlow and Firecookies) I recognize, but those two are unfamiliar to me.

By: billwscott

billwscott — Mon, 23 Jun 2008 15:59:33 +0000

Thanks Dion. A few points:
*) At Netflix we are using a full cycle tracing mechanism that at the time does not include Jiffy-Web. This gives us backend to end of rendering timings. Jiffy-Web measures only on the client.

*) Jiffy-Web provides a simple API to do a common task (time stamp) as well as provide a way to log to a logging service

*) As Dion mentioned, this firebug panel accessing the logging information that is contained in a JSON object in the measured page

*) The firebug panel can actually work with any tool like this by setting three firefox configuration parameters (see the documentation). I am interested in other ways to work with external measuring products (or even extending firebug’s console method to write to this panel).

*) I have a separate firebug tool that is internal to netflix that visualizes this full cycle information. I will be merging the two firebug tools into one… but need a standard definition for measurements so the tool can graph anyone’s measures.

*) Jiffy-Web will be “released” sometime today in concert with Scott Ruthfield’s talk at Velocity.

*) As far as fine-grained, with any measuring there is some milliseconds wasted by having to do this in javascript. You can minimize this of course. But I have found the best measurement happens in the aggregate with statistically applied measures. But the purpose of tools like this is to give you an indication of whether you are screwing something up and possibly where to focus your tuning efforts.

By: lennym

lennym — Mon, 23 Jun 2008 15:10:33 +0000

At first glance this looks like it could be a very useful tool, however with such things I am concerned that there is the potential to be a slight “uncertainty principle” effect, by which the tools used to measure performance, conversely affect performance.

I’ve certainly had issues with Firebug causing performance issues with animations, and anyone using gmail will have seen the warning displayed when you try and access the page with FireBug enabled.

My point basically is that quite how ‘fine-grained’-ly can we measure performance without making the results meaningless?