The Garbage Collector relies on information compiled into your assembly provided by the JIT compiler that tells it what code address ranges various variables and “things” are still in use over. As such, in your code, since you no longer use the object variables GC is free to collect them. WeakReference will not prevent this, … Read more
A class in Java can be garbage-collected when nothing references it. In most simple setups this never happens, but there are situations where it can occur. There are many ways to make a class reachable and thus prevent it from being eligible for GC: objects of that class are still reachable. the Class object representing … Read more
In Sun’s JVM, last I knew, the entire heap must be allocated in a contiguous address space. I imagine that for large heap values, it’s pretty hard to add to your address space after startup while ensuring it stays contiguous. You probably need to get it at startup, or not at all. Thus, it is … Read more
To be precise, garbage collectors are a problem for real-time systems. To be even more precise, it is possible to write real-time software in languages that have automatic memory management. More details can be found in the Real Time Specification for Java on one of the approaches for achieving real-time behavior using Java. The idea … Read more
So the concern for “real time” is the latency introduced by GC collections. GHC uses a multicore garbage collector (and there is a branch with per-thread local heaps). Originally developed to improve multcore performance (each core can collect independently) by reducing the cost of frequent stop-the-world synchronisation, this happens to also benefit soft-real time for … Read more
The del statement doesn’t reclaim memory. It removes a reference, which decrements the reference count on the value. If the count is zero, the memory can be reclaimed. CPython will reclaim the memory immediately, there’s no need to wait for the garbage collector to run. In fact, the garbage collector is only needed for reclaiming … Read more
The initial heap size is the minimum heap size. It won’t get smaller than the initial heap size. From Tuning Garbage Collection with the 5.0 Java[tm] Virtual Machine: By default, the virtual machine grows or shrinks the heap at each collection to try to keep the proportion of free space to live objects at each … Read more
Can Java finalize an object when it is still in scope? Yes. However, I’m being pedantic here. Scope is a language concept that determines the validity of names. Whether an object can be garbage collected (and therefore finalized) depends on whether it is reachable. The answer from ajb almost had it (+1) by citing a … Read more
PermGen is replaced with Metaspace in Oracle/Sun JDK8, which is very similar. The main difference is that Metaspace can expand at runtime.
To classify things, lets define the memory layout and then talk about how GC works. Memory Layout In Erlang, each thread of execution is called a process. Each process has its own memory and that memory layout consists of three parts: Process Control Block, Stack and Heap. PCB: Process Control Block holds information like process … Read more