Mark Lam's Blog: June 2007 Archive

There are times in the course of your development effort when your application just seems to hang forever. At those times, you wish you had some way of knowing where the hang is occurring. If you're running on JavaSE, chances are you'll have a lot of advanced tools that makes life easy for you. But if you're running on an embedded device, suddenly, your options are now severely limited. For the phoneME Advanced VM (CVM), there's a way to get help on this even when there is not advance debugging support on your device.

What I'll be showing here is an old trick to get an asynchronous dump of the stacks of all the threads that are currently alive in the VM. First of all, you need to know that this is a hack i.e. it's not good and clean code. That's why I haven't already committed it to the source repository, and won't be doing so. The reason it is a hack will be explained below later under Why this is a Hack!!!. But even though it is a hack, it is useful when you need it. Many of my colleagues as well as customers have often asked me for the code patch for this hack to help with debugging the hangs in their applications. I figure you might find it helpful too.

So, here it is ...

The Price of Speed

Posted by mlam on June 06, 2007 at 11:40 PM | Permalink | Comments (1)

I apologize for not writing in a while. I've been trying to get some real work done (i.e. coding and designing solutions to improve the lives of our customers ... or at least, that's my goal). Anyway, two weeks ago, an interesting comment was added to a previous article I wrote on understanding JIT performance. The comment says ...

"Very informative blog!! Is there any information/projection on what % of apps in handheld market is based on and is expected to be written in Java/J2ME? I hear that, since handhelds are very memory constrained, JIT has challenges wrt to space and energy consumption. Is that too high to keep JIT technology in the darkages? How much more memory does JIT add over an interpreted version? Is there any study or white paper on why and how much such an overhead would be for JIT?"

Thanks for the comment (and the compliment), Cochin. I wanted to answer right away, but alas, I needed to gather some facts for it, and my day job also got in the way (needed to get some work done). At this moment, while I'm waiting for my computer to crunch some major compilations, I'll take a few minutes to give you my answer ...

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