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Asked: 2026-05-15T23:53:36+00:00

Suppose we do a malloc request for memory block of size n where 2

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Suppose we do a malloc request for memory block of size n where 2 ^k !=n for k>0.
Malloc returns us space for that requestted memory block but how is the remainig buffer handled from the page. I read Pages are generally blocks of memory which are powers of two.

Wiki states the following:

 Like any method of memory allocation, the heap will become fragmented; that is,
 there will be sections of used and unused memory in the allocated 
 space on the heap. A good allocator will attempt to find an unused area
 of already allocated memory to use before resorting to expanding the heap.

So my question is how is this tracked?

EDIT: How is the unused memory tracked when using malloc ?

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1 Answer

  1. Editorial Team

    This really depends on the specific implementation, as Morten Siebuhr pointed out already. In very simple cases, there might be a list of free, fixed-size blocks of memory (possibly all having the same size), so the unused memory is simply wasted. Note that real implementations will never use such simplistic algorithms.

    This is an overview over some simple possibilities: http://www.osdcom.info/content/view/31/39/

    This Wikipedia entry has several interesting links, including the one above: http://en.wikipedia.org/wiki/Dynamic_memory_allocation#Implementations

    As a final remark, googling “malloc implementation” turns up a heap (pun intended) of valuable links.

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