IBM User Guide for Java V7 on Windows > Troubleshooting and support > Problem determination > Windows problem determination > Debugging memory leaks

The Windows memory model

Windows memory is virtualized. Applications do not have direct access to memory addresses, so allowing Windows to move physical memory and to swap memory in and out of a swapper file (called pagefile.sys).

Allocating memory is usually a two-stage process. Just allocating memory results in an application getting a handle. No physical memory is reserved. There are more handles than physical memory. To use memory, it must be 'committed'. At this stage, a handle references physical memory. This might not be all the memory you requested.

For example, the stack allocated to a thread is usually given a small amount of actual memory. If the stack overflows, an exception is thrown and the operating system allocates more physical memory so that the stack can grow.

Memory manipulation by Windows programmers is hidden inside libraries provided for the chosen programming environment. In the C environment, the basic memory manipulation routines are the familiar malloc and free functions. Windows APIs sit on top of these libraries and generally provide a further level of abstraction.

For a programmer, Windows provides a flat memory model, in which addresses run from 0 up to the limit allowed for an application. Applications can choose to segment their memory. In a dump, the programmer sees sets of discrete memory addresses.

Parent: Debugging memory leaks

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