Memory Allocation APIs

Intel® VTune™ Amplifier provides a set of APIs to help it identify the semantics of your malloc-like heap management functions.

Annotating your code with these APIs allows VTune Amplifier to correctly determine memory objects as part of Memory Access Analysis.

Usage Tips

Follow these guidelines when using the memory allocation APIs:

  • Create wrapper functions for your routines, and put the __itt_heap_*_begin and __itt_heap_*_end calls in these functions.

  • Allocate a unique domain for each pair of allocate/free functions when calling __itt_heap_function_create. This allows the VTune Amplifier to verify a matching free function is called for every allocate function call.

  • Annotate the beginning and end of every allocate function and free function.

  • Call all function pairs from the same stack frame, otherwise the VTune Amplifier assumes an exception occurred and the allocation attempt failed.

  • Do not call an end function without first calling the matching begin function.

Using Memory Allocation APIs in Your Code

Use This

To Do This

typedef void* 
__itt_heap_function;
 
__itt_heap_function 
__itt_heap_function_create( 
      const __itt_char* <name>, 
      const __itt_char* <domain> ); 

Declare a handle type to match begin and end calls and domains.

  • name = Name of the function you want to annotate.

  • domain = String identifying a matching set of functions. For example, if there are three functions that all work with my_struct, such as alloc_my_structs, free_my_structs, and realloc_my_structs, pass the same domain to all three __itt_heap_function_create() calls.

void __itt_heap_allocate_begin( 
   __itt_heap_function <h>, 
   size_t <size>, 
   int <initialized> );
 
void __itt_heap_allocate_end( 
   __itt_heap_function <h>, 
   void** <addr>, 
   size_t <size>, 
   int <initialized> ); 

Identify allocation functions.

  • h = Handle returned when this function's name was passed to __itt_heap_function_create().

  • size = Size in bytes of the requested memory region.

  • initialized = Flag indicating if the memory region will be initialized by this routine.

  • addr = Pointer to the address of the memory region this function has allocated, or 0 if the allocation failed.

void __itt_heap_free_begin( 
   __itt_heap_function <h>, 
   void* <addr> );
 
void __itt_heap_free_end( 
   __itt_heap_function <h>, 
   void* <addr> ); 

Identify deallocation functions.

  • h = Handle returned when this function's name was passed to __itt_heap_function_create().

  • addr = Pointer to the address of the memory region this function is deallocating.

void __itt_heap_reallocate_begin( 
   __itt_heap_function <h>, 
   void* <addr>, 
   size_t <new_size>, 
   int <initialized> );
 
void __itt_heap_reallocate_end( 
   __itt_heap_function <h>, 
   void* <addr>, 
   void** <new_addr>, 
   size_t <new_size>, 
   int <initialized> ); 

Identify reallocation functions.

Note that itt_heap_reallocate_end() must be called after the attempt even if no memory is returned. VTune Amplifier assumes C-runtime realloc semantics.

  • h = Handle returned when this function's name was passed to __itt_heap_function_create().

  • addr = Pointer to the address of the memory region this function is reallocating. If addr is NULL, the VTune Amplifier treats this as if it is an allocation.

  • new_addr = Pointer to a pointer to hold the address of the reallocated memory region.

  • size = Size in bytes of the requested memory region. If new_size is 0, the VTune Amplifier treats this as if it is a deallocation.

Usage Example: Heap Allocation

#include <ittnotify.h>

void* user_defined_malloc(size_t size);
void user_defined_free(void *p);
void* user_defined_realloc(void *p, size_t s);

__itt_heap_function my_allocator;
__itt_heap_function my_reallocator;
__itt_heap_function my_freer;

void* my_malloc(size_t s)
{
    void* p;

    __itt_heap_allocate_begin(my_allocator, s, 0);
    p = user_defined_malloc(s);
    __itt_heap_allocate_end(my_allocator, &p, s, 0);

    return p;
}


void my_free(void *p)
{
    __itt_heap_free_begin (my_freer, p);
    user_defined_free(p);
    __itt_heap_free_end (my_freer, p);
}

void* my_realloc(void *p, size_t s)
{
    void *np;

    __itt_heap_reallocate_begin (my_reallocator, p, s, 0);
    np = user_defined_realloc(p, s);
    __itt_heap_reallocate_end(my_reallocator, p, &np, s, 0);

    return(np);
}

// Make sure to call this init routine before any calls to
// user defined allocators.
void init_itt_calls()
{
    my_allocator = __itt_heap_function_create("my_malloc", "mydomain");
    my_reallocator = __itt_heap_function_create("my_realloc", "mydomain");
    my_freer = __itt_heap_function_create("my_free", "mydomain");
}
For more complete information about compiler optimizations, see our Optimization Notice.
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