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> Any GC uses much less memory than a refcount or malloc application. That's plain wrong. > because it's much too hard to do that by yourself. Too hard to do
by rstuart4133 9y ago
> Any GC uses much less memory than a refcount or malloc application.
That's plain wrong.
> because it's much too hard to do that by yourself.
Too hard to do yourself? There are some of us who have been doing it for decades. In places where performance, predictable runtime and memory usage is of paramount importance (like the linux kernel) it is still done manually. I'll grant you Moore's law has made those places increasing rare nowadays.
Yes it harder to do it manually, but only in the sense that it's harder to do anything manually than have it automated. But being hard and error prone doesn't mean the result is slower, or uses more memory. A moments thought should have told you that. GC delays freeing memory until there is sufficient memory pressure. The mental load imposed by tracking malloc's means a programmer does it immediately so he can forget about it. Thus the memory is available for re-use immediately.
In my experience a long running program manually managing it's heap has a heap about twice the size of actual space in use. In theory some degenerate cases caused by fragmentation can make it far worse - but I've never been bitten by it. Long running GC languages (they tend to be written in Java) it's around 5 times. Again, if you done any sort of server administration, you would know this. All of us who do have watched Java VM's grow over with amazement and dismay. Ironically, the cure is a form of manual memory management - kill them and restart.