Mali-760 MP2 gpu memory usage per process

Hi, expert,

I am using the phone of MEILAN, which use soc of MT6752 with mali-760 mp2, I want to track process gpu memory usage and found there is a debug node "/d/mali/gpu_memory" which record each process context gpu memory usage.  I found that the data is smaller as expected. So I wrote an test apk which allocates an 4M texture(1024*1024 RGBA) each time I touch the screen, but the gpu memory of the test app increase only 1M each time.  I also tracked the /proc/meminfo, found the free memory decrease about 4M.   so the data of the node "/d/mali/gpu_memory"  are not real gpu memory usage?