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Dalvik patch for Facebook for Android

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Re: Dalvik patch for Facebook for Android

#11

Post by saljam »

jerf wrote: post #7
MichaelGG wrote: post #5

Certainly if there's a lot of small methods, they could have an optimization pass that inlines some of them and bring their overall method count down. I wouldn't be surprised if that was a small performance gain, too.

I thought of that, then the pragmatic engineer in me observed that they only discovered this after cracking their app into so many small methods. Given the time choice of 1. uncracking their app into small methods (which presumably wasn't atomic, so now that's all mixed in with other development, so it's not like it can just be reverted) or 2. hacking the system to handle more methods, I am forced to admit that choic…

I think the OP meant automatic inlining. I.e. by a compiler.

Re: Dalvik patch for Facebook for Android

#12

Post by marhumph »

saidajigumi wrote: post #4
[deleted] wrote: post #2

[deleted]

If you read TFA, they bent over backwards to attempt app-only methods... but ultimately hit a hard wall on the LinearAlloc buffer size in Android 2.x. So, off to extraordinary measures land they went.

No, they went off down a path, and then found that their approach didn't work on one of their target devices.

If they had known about this hard wall in one of their target devices, before making and implementing their code design choices, would they have taken the same approach?

What they did is neat, why they did, given their journey, is understandable, how they frame what they did and how they did it is masturbatory.

Re: Dalvik patch for Facebook for Android

#13

Post by barbs »

I really love reading recounts like this. Seeing other developers try, fail, and try again to come up with creative solutions for difficult problems, and then finally arriving at a solution, is so satisfying. It really demonstrates how creativity is manifested in programming, and is truly inspiring.

A favourite of mine is Jari Komppa's article on his process of porting Death Rally from DOS to Windows: http://sol.gfxile.net/dr_gdm.html.

Does anyone have any other articles along the same lines? I'd love to read them!

Re: Dalvik patch for Facebook for Android

#15

Post by ajtaylor »

I can't tell if I should be excited for the developers to have been so clever, or horrified with all the hacks they had to incorporate to make it work. Either way, the new FB app is definitely an improvement over the older version (lag central!). Is it reasonable for the OS to make such a low-level component configurable so this type of convolutions aren't required?

Re: Dalvik patch for Facebook for Android

#16

Post by ajtaylor »

cek wrote: post #3

It's interesting to see the parallels between Android and Windows in this regard. Here's a story from my past, copied from a blog post I wrote last year: My first job at Microsoft was providing developer support for the early Windows SDKs. To do my job well, I spent hours studying the Windows SDK documentation, the Windows source code, and writing sample applications. I then spent hours poring over customers’ (such a…

As soon as you mentioned "Adobe Type Manager" I remembered reading about this case some time ago. But knowing it was you that discovered this makes it all the better. If only we could create perfect APIs the first time around...

Re: Dalvik patch for Facebook for Android

#17

Post by blinkingled »

cek wrote: post #3

It's interesting to see the parallels between Android and Windows in this regard. Here's a story from my past, copied from a blog post I wrote last year: My first job at Microsoft was providing developer support for the early Windows SDKs. To do my job well, I spent hours studying the Windows SDK documentation, the Windows source code, and writing sample applications. I then spent hours poring over customers’ (such a…

Came here to opine on the exact same topic! I was going to dig up some Raymond Chen blog entries but your CreateFont example illustrates it equally well. I guess hacks are inevitable when you are dealing with that kind of scale/complexity.

Re: Dalvik patch for Facebook for Android

#19

Post by jmillikin »

According to http://techcrunch.com/2013/03/04/facebook-google-dalvik/ and http://venturebeat.com/2013/03/04/google-facebook-android/ , the specific limit being hit was a cap of three million methods per instance of the Dalvik VM.

Wisdom of a three-million-method app aside, I wonder why they didn't fix this in the compilation toolchain rather than by poking around in native memory areas during app startup. Facebook wrote a PHP->C++ compiler; changing the Dalvik compiler to more aggressively inline small methods seems trivial in comparison.

Re: Dalvik patch for Facebook for Android

#20

Post by mikeash »

marhumph wrote: post #8

The first paragraph is just rampant self praise. Basically these engineers decided to be really clever, painted themselves into a corner, smashed a hole in the wall so as to escape from said corner, and then bragged about how great they are.

Hitting an arbitrary (and undocumented?) platform limit on the number of methods your app is allowed to have is hardly "painting themselves into a corner".
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