delete PG, memory does not released

i use the following code to delete PG object:

delete mPage->getPageLoader();
delete mPage;

but the memory was not completely released as PG used,

so, when i shut down the scene and reload it time and time angain,

the memory will become big and big.

how to release its memory completely ?

i found that the ImpostorPage can not be delete completely,

if i don't add the ImpostorPage to PG, when delete the PG, it can release all memory,

but i debug it , and do not see any bugs, any body help me ?