GC vs. Manual Memory Management Real World Comparison

[Paulo Pinto]

On Wednesday, 24 October 2012 at 18:26:48 UTC, Rob T wrote:
> On Wednesday, 24 October 2012 at 12:21:03 UTC, Paulo Pinto 
> wrote:
>>
>> Having dealt with systems programming in languages with GC 
>> (Native Oberon, Modula-3), I wonder how much an optional GC 
>> would really matter, if D's GC had better performance.
>>
>> --
>> Paulo
>
> Well, performnce is only part of the GC equation. There's 
> determinism, knowing when the GC is invoked and ability to 
> control it, and increased complexity introduced by a GC, which 
> tends to increase considerably when improving the GCs 
> performance and ability to manage it manually. All this means 
> there's a lot more potential for things going wrong, and this 
> cycle of fixing the fix may never end.
>
> The cost of clinging onto a GC may be too high to be worth 
> relying on as heavily as is being done, and effectivly forcing 
> a GC on programmers is the wrong approach because not everyone 
> has the same requirements that require its use. When I say 
> "forcing", look at what had to be done to fix the performance 
> of the game in question, what was done to get rid of the GC was 
> a super-human effort and that is simply not a practical 
> solution by any stretch of the imagination.
>
> A GC is both good and bad, not good for everyone and not bad 
> for everyone, with shades of gray in between, so it has to be 
> made fully optional, with good manual control, and easily so.
>
> --rt

I do understand that.

But on the other hand there are operating systems fully developed 
in such languages, like Blue Bottle,

http://www.ocp.inf.ethz.ch/wiki/Documentation/WindowManager

Or the real time system developed at ETHZ to control robot 
helicopters,

http://static.usenix.org/events/vee05/full_papers/p35-kirsch.pdf

I surely treble at the thought of a full GC collection in plane 
software. On the other hand I am old enough to remember the 
complaints that C was too slow and one needed to write everything 
in Assembly to have full control of the application code.

Followed by C++ was too slow and one should use C structs with 
embedded pointers to have full control over the memory layout of 
the object table, instead of strange compiler generated VMT 
tables.

So I always take the assertions that manual memory management is 
a must with a grain of salt.

--
Paulo