Subtracting one snapshot from another snapshot is a useful way to find memory leaks and memory spikes. It can show you everything that was allocated and freed in a time range.
How to Use:
- Take two snapshots and then click on the 'Subtract Snapshots' button (or from the tools menu).
- You will then see a dialog where you can select the two snapshots that you are interested in.
- This will create a new snapshot which will be displayed in the snapshot list view.
- You can then view this snapshot just like any other snapshot.
- Note that the snapshot may contain negative values if some call sites have freed more than they have allocated.
Subtracting using the graph view
There is a quick way to achieve the above using the graph view. Right click at the start of the range you are interested in and drag the mouse to the end of the range. You will see a blue transparent rectangle.
MemPro will automatically take a snapshot at the start and end of this range, and create a new snapshot that is a subtraction of the two snapshots.
These new snapshots will appear in the snapshot list view and you can view them in the normal way.