Monthly Archives: November 2009

Over the last couple days I noticed my Firefox getting painfully slow. The weird part was that the rest of my system was responsive. When I opened Activity Monitor it showed 100% CPU usage for Firefox. I decided to do some investigating. I used the ‘Sample Process’ feature in Activity Monitor.  After setting the display to ‘Percent of Parent’ I noticed that there was a lot of ‘Flash_EnforceLocalSecurity’ messages which lead me to believe that Flash was the culprit.

I went through my tabs, and sure enough I had lots of Flash open. This pattern kept repeating itself. I’d notice Firefox getting sluggish, close flash web pages and see Firefox performing properly and CPU usage levels back to normal. I found it strange that I could play Hulu and Youtube videos fine. I even went to www.bannerserver.com and found that while Firefox was never using 100% of my CPU. This was baffling me until I figured out what the problem was. This issue only happens when AT&T Uverse flash ads show up.

Not everyone cares to find the root cause of a problem like this. It is also only sporadically reproducible, going to the same website might show different ads each time. I would bet that a lot of people would look at this and say “Firefox is slow”, especially because the ads are there on many different pages.  These ads are also not the primary reason someone goes to the page (I’d hope) which means that it is difficult to associate the flash ad with the purpose of their tab if they do try to figure out what the problem is. Having plug-ins in a separate process (Electrolysis) seems like a great idea. I hope that, like Safari on Mac, it shows up as a totally separate process which helps avoid people blaming Firefox for poor performance.

The most annoying part of this whole situation is that I’d love to be a Uverse subscriber.  It is bad enough that they aren’t offering it in my area, but to make my browser slower is a slap in the face!

During the lead up to the Firefox 3.5 release, there was a request to have older machines running unit tests. Our solution for the 3.5 release was to burn Ted cycles. This is unfortunate because Ted could have otherwise done much more useful things. For the Firefox 3.6 release, we automated this testing. The reason for running these tests is that our JavaScript interpreter spits out native machine code . The problem is that there are still machines capable of running Firefox but do not have all of the latest instruction sets(MMX, 3DNow, SSE2, SSE3, ad infinitum). Specifically, there was a concern over the inclusion of the SSE2 instructions when running on non-SSE2 capable hardware. This is especially important for those people who are still running an older machine exclusively for browsing. It is very important that we don’t unknowingly introduce a requirement for SSE2. We also need to test our claimed compatibility with older Macintosh machines based on the PowerPC core. To fix this situation, I have created the geriatric master. This master is in charge of our fleet of aging fleet of Pentium 3s and PowerPC G4s. It reports to the GeriatricMasters tinderbox. I currently am monitoring the Mozilla 1.9.2 and Mozilla Central nightly builds.

These are the first two succesful runs

We are running some old machines saved from the Landings to Castro move. The P3s are around a decade old and the G4 Mac Mini and Dual G4 PowerMacs are about 4-5 years old. We also aren’t running matched hardware which is going to make detective work on failures difficult. I have found some machines to replace our mixture of P3s that do not even have SSE. They are based on the AMD Geode LX800 processor. These machines are what the OLPC XO have as a cpu. Because they are based on an ancient CPU core (Cyrix 5×86, technically a 486), they even lack SSE. That makes them the perfect for our testing. The model that I am looking at is the MSI Fuzzy. I don’t really understand their naming, but this machine would fit our needs perfectly. It has a fast (for the category) processor and slots for 1gb of ram. Most importantly, it allows us to have as many identical machines as we need. The Mac Mini is easier to standardize on because it was fairly popular at the time and there are only one or two minor variations of the PowerPC Mini.

Before we go rushing out and buying a bunch of new machines for this testing, we need to know how long there will be demand for this kind of testing. I would estimate that it would cost about $500 per Geode machine, and that we might be able to get nightly coverage on two to three branches on linux and windows with four machines.

Also of note is that because we are running on such old hardware, we are getting JavaScript timeouts. I don’t really know how to manually set the preference that ignores these timeout warnings, but it is causing a lot of the jobs to be killed off because they aren’t responsive. I’d love to know if you know how I can disable this in an easy to automate way. I was thinking that I could launch and kill Firefox to create a profile, modify the profile’s preference file then launch it again for the real tests. I don’t know which preference file I would need to do this on though.

This is where I’d like to ask people who are working on the JavaScript JIT to let me know how long we need to do this testing and whether this current coverage (mozilla192 and mozilla-central) is enough. A comment on this post, bug 463262 or ping me on #build (jhford).

As a side note, this configuration makes it possible for us to run unit tests on second tier support machines and operating systems. If there is any community interest, I can look making it possible for anyone to connect their machine to this buildbot master if they have an obscure machine with spare cycles. This would require you to be able to dedicate the box for this testing, us to already produce builds that run on that architecture.

If anyone wants, I can get some photos of the machines on Monday.