HELP : Rss and Pss pages are always 0 for some drivers. Why?

[Pintu Agarwal <pintu_agarwal@yahoo.com>]

Dear All,
 
I have a problem regarding RSS and PSS pages always showing zero for some PID.
 
We are using customized kernel2.6.36 (arm with no swap).
 
We are having a menu-screen application (current PID 1939)
 
When I do cat /proc/1939/smaps we are getting "Rss", "Pss" page as always zero for some of the modules  /dev/ump and /dev/mali.
The output is as follows:-
cat /proc/1936/smaps | grep -A 11 /dev/ump
43698000-43810000 rw-s 0000e000 00:11 6751       /dev/ump
Size:               1504 kB
Rss:                   0 kB
Pss:                   0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Swap:                  0 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
----------------------------------------------------------------------
 
I wanted to understand why Rss and Pss pages information for only /dev/ump (similarly for /dev/mali) is not shown correctly by smaps.
Where could be the problem and where I should debug?
 
Any information on this will be a great help.
 
 
 
Thanks, Regards,
Pintu Kumar

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