Realtime Priority Applications And Windows NT (103810)

SUMMARY

An application that is running in the RealTime priority class (a base priority of 16) can potentially take so much of the available CPU resources that no resources will be available for other processes or threads. This includes a possible "starving" of both the mouse and keyboard. This implies that the mouse may become unavailable to click another application to execute an action. It also implies that the keyboard may not respond if you try to press CTRL+ESC to get the Task List and Cancel the application.

To run a process or thread in the RealTime priority class requires that you either be an administrator, a member of the administrator's group, or have the Increase Scheduling Priority user right (SeIncreaseBasePriorityPrivilege) explicitly granted to you. Administrators must use caution when granting this right to users.

MORE INFORMATION

Only Windows 32-bit applications can be scheduled for RealTime and High priorities. Windows 16-bit, MS-DOS, OS/2, and POSIX applications may only run at a priority of Normal (maximum base priority of 7). Also, if a process has a Low priority, all processes spawned from it (children) will inherit the Low priority, but if the process has a High priority, all children will be assigned a Normal priority.

   Default Priority Bases
   ----------------------

   Low:        4
   Normal:     7
   High:      13
   RealTime:  24

Note that many items can influence this base priority, including user groups (administrators versus users), how tasking is set up in the Control Panel System option, and whether the application is in the foreground or background.