When you configure the memory and on your system if other applications are also present, in such cases de-allocation of memory may impact huge performance issue. so lock page memory is useful here as to prevent/reserve the memory for Sql server.
1. Run “secpol.msc” from windows run dialog -Local Security Setting
2. Expand “Local Policies” in the left pane
3. Click “User Rights Assignment”
4. Double-click “”Lock Pages in Memory”
5. In the “Local Security Setting” page, please check if the account used by SQL Server in the list box
this feature will lock the pages in memory by that users/account -(sql server is running)
Following is the link which shows how to configure Lock page memory.