new principle of division between structures and classes

[Benji Smith]

Andrei Alexandrescu wrote:
> Benji Smith wrote:
>> Actually, memory allocated in the JVM is very cache-friendly, since 
>> two subsequent allocations will always be adjacent to one another in 
>> physical memory. And, since the JVM uses a moving GC, long-lived 
>> objects move closer and closer together.
> 
> Well the problem is that the allocation size grows quickly. Allocate and 
> dispose one object per loop -> pages will be quickly eaten.
> 
> for (...) {
>     JavaClassWithAReallyLongNameAsTheyUsuallyAre o = factory.giveMeOne();
>     o.method();
> }
> 
> The escape analyzer could catch that the variable doesn't survive the 
> pass through the loop, but the call to method makes things rather tricky 
> (virtual, source unavailable...). So then we're facing a quickly growing 
> allocation block and consequently less cache friendliness and more 
> frequent collections.
> 
> 
> Andrei

Good point. I remember five years ago when people were buzzing about the 
possible implementation of escape analysis in the next Java version, and 
how it'd move a boatload of intermediate object allocations from the 
heap to the stack. Personally, I don't think it'll ever happen. They 
can't even agree on how to get *closures* into the language.

I personally think the JVM and the HotSpot compiler are two of the 
greatest accomplishments of computer science. But the Java community has 
long since jumped the shark, and I don't expect much innovation from 
that neighborhood anymore.

--benji