Visual Studio Hacks [Electronic resources] نسخه متنی

Hack 67. Profile Heap Allocations

Use the Allocation Profiler to research how
your objects are being handled on the heap.

This hack is an introduction to the Allocation Profiler tool available
at Figure 7-39.

Figure 7-39. AllocationProfiler

The Profiling Active box should be checked and Allocations should be
chosen from the Profile radio button list on the right.

Choose Profile Application from the File menu and browse to
AP_example1.exe.

The Allocation Profiler will execute your application and log
everything that goes through the garbage collector. When the
application has finished executing, it will automatically launch the
Allocation Graph, which is shown in Figure 7-40.

Figure 7-40. Allocation Graph

The Scale option allows you to choose the number of pixels to display
proportional to allocated memory.

The Detail option shows more objects the lower you go in the scale.
If you choose 0 (everything), you will see every object allocated. By
choosing 20 (coarse), you will get a higher-level view of the core
objects in your application.

Figure 7-40 shows you a hierarchical drill-down of
the managed memory
allocated in your application. In this example, the application has
allocated 126 KB of managed memory. Of the initial 126 KB (100%), 117
KB (93.15%) has been initialized from the AP_example1::Main method.
Since the only thing in the main method was a loop creating the
AP_example_class object,
AP_example1.AP_example_class is also 117 KB
(93.15%) of the managed memory in the application.

The lowest levels of objects in the graph represent the percentage of the entire application, not the percentage of their parent.

From the main menu, choose View Histogram Allocated Types.
The result is shown in Figure 7-41.

Figure 7-41. Histogram allocated types

Figure 7-41 shows you kilobytes allocated by object.
By hovering over each item in the histogram, it will show you the
number of instances created and their average size. You can
right-click on the bar to show where the instance(s) were allocated
and export the data.

From the main menu, choose View Objects by Address to open
the window shown in Figure 7-42.

Figure 7-42. View Objects by Address window

In Figure 7-42, each vertical bar shows you an
address range for each GC heap. There are two heaps for the system
build, the normal heap and the large object heap. In this example, if
you hover over the first bar in the graph, it will show you the
object address for each instance you allocated. In addition, it will
show you the size (in bytes) and how long the object was allocated in
memory.

From the main menu, choose View Histogram by Age, which is
shown in Figure 7-43.

Figure 7-43. Histogram by Age window

In Figure 7-43, each vertical bar in this graph
shows you a histogram of created objects by time. The time the object
was in memory determines which bucket the object''s
instance will be included in.

From the main menu, choose View Time Line, which is shown
in Figure 7-44.

Figure 7-44. View Time Line window

In Figure 7-44, the vertical axis of this chart
shows you the memory addresses allocated. The horizontal axis shows
you the time in which they were allocated. In this example, somewhere
around .2 seconds into the application, almost 100% of the objects
were allocated. You can right-click at any point in the timeline to
view objects by address at that time or by any of the recent features
I covered in this hack.

The preceding example was intended to show you the analysis the
Allocation Profiler provides. In a real-life application, you would
use the Allocation Profiler to verify that the allocated objects are
the ones you expected, view potential memory
leaks, view how long objects are on the GC heap, and view what
percentage each object allocates in your overall application memory
usage. For more information, download the Allocation Profiler from
and refer to the included
documentation.

Jayme Davis