Re: [Vala] Port Tomboy?

[James Livingston <doctau mac com>]

On 28/06/2009, at 1:57 AM, Jiří Zárevúcky wrote:
> Wrapped native code is generally slower and more difficult to work
> with then a pure CIL implementation. The library in question would be
> more likely to exist in two separately maintained versions.


There are several good reasons to convert to native code, but  I think  
"performance" is probably one of the worst. Modern VMs produce  
reasonably efficient code for the hotspots that they consider to be  
worth optimising, and there are actually quite a few optimisations  
they can do at runtime that statically compiled native code can't[0].

99% of your code isn't going to be the performance sensitiv, and as  
Jiří mentioned crossing the VM<->Native boundary can potentially be  
more expensive than having it all in the VM. it's not always, and  
there are times when native code will still be faster, but it's not in  
every case.


I don't know a lot about .Net and Mono, as I come from a Java/JVM  
background, and there are cases where performance sensitive code can  
actually be faster running in a VM than statically compiled.

Say for example you have a library which needs to be thread safe, and  
so has locking code in various places. With native code, you're going  
to be paying the price of the locking even if you application (or the  
part of it that uses the library) is single threaded. Recent JVMs are  
smart enough to realise this and won't even bother to allocate a lock  
until a second thread touches an object created by a different one.


I'm not saying you shouldn't port code from one language to another,  
but make sure you have your reasons right :)


[0] well, native code can do them in the possible on a Turing machine  
sense, but not practically.

--
James