Intel® VTune™ Profiler User Guide

User Guide

Contents

Memory Allocation APIs

Intel® VTune™
Profiler
 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
Profiler
 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
    Profiler
     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
    Profiler
     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
Profiler
 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
    Profiler
     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
    Profiler
     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");
}

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.