A question on AM1810 DP data loss

Here is another question my team is facing now. 

AM1810: Linux 2.6.33.7-rt29

DP: DPSlave_EVAL in am181x_profibus_dpslave_app-04.01.00.00

PLC  Profibus Master communicates with AM1810  PROFIBUS  slave within a period of 20 ms. DP slave station can work normally when there is no other Linux application program works. But when other program works, such as ntupdate for timing or Web access to AM1810 module, data loss will occasionally happen to DP slave. The time will last several to decades of periods and thus DPSlave_EVAL real-time performance will suffer to some extent. But this phenomenon doesn't happen everytimen when our engineers start such programs.

So, how to ensure DPSlave_EVAL to work real-time without being affected by other such programs' functioning? It is a safety issue for our controlling system and thus we want to avoid from this kind of DP data loss.

Thank you very much.

Guotao