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3.2.3.9 Statistics for Memory Allocation with malloc

You can get information about dynamic memory allocation by calling the mallinfo2 function. This function and its associated data type are declared in malloc.h; they are an extension of the standard SVID/XPG version.

Data Type: struct mallinfo2 ¶

This structure type is used to return information about the dynamic memory allocator. It contains the following members:

size_t arena

This is the total size of memory allocated with sbrk by malloc, in bytes.

size_t ordblks

This is the number of chunks not in use. (The memory allocator size_ternally gets chunks of memory from the operating system, and then carves them up to satisfy individual malloc requests; see The GNU Allocator.)

size_t smblks

This field is unused.

size_t hblks

This is the total number of chunks allocated with mmap.

size_t hblkhd

This is the total size of memory allocated with mmap, in bytes.

size_t usmblks

This field is unused and always 0.

size_t fsmblks

This field is unused.

size_t uordblks

This is the total size of memory occupied by chunks handed out by malloc.

size_t fordblks

This is the total size of memory occupied by free (not in use) chunks.

size_t keepcost

This is the size of the top-most releasable chunk that normally borders the end of the heap (i.e., the high end of the virtual address space’s data segment).

Function: struct mallinfo2 mallinfo2 (void) ¶

Preliminary: | MT-Unsafe init const:mallopt | AS-Unsafe init lock | AC-Unsafe init lock | See POSIX Safety Concepts.

This function returns information about the current dynamic memory usage in a structure of type struct mallinfo2.