Panchaleswar Nayak's Weblog

The porpose of writing these docs are to educate the community about the real time aspect of Solaris Operating System.Step by Step I will try to write how we can use solaris for running realtime applications. Basic Rules of Real-time Applications. Real-time response is guaranteed when certain conditions are met. In This section I will discuss these conditions and some of the more significant design errors. Most of the potential problems described here can degrade the response time of the system. One of the potential problems can freeze a workstation. Other, more subtle,mistakes are priority inversion and system overload. A Solaris real-time process has the following characteristics: Runs in the RT scheduling class, as described in “The Real-Time Scheduler”. Locks down all the memory in its process address space. The Real-Time Scheduler Interface Calls That Control Scheduling Using priocntl Control over scheduling of active classes is done with priocntl(2). Class attributes are inherited through fork(2) and exec(2), along with scheduling parameters and permissions required for priority control. This inheritance happens with both the RT and the TS classes. priocntl(2) is the interface for specifying a real-time process, a set of processes, or a class to which the system call applies. priocntlset(2) also provides the more general interface for specifying an entire set of processes to which the system call applies. The command arguments of priocntl(2) can be one of: PC_GETCID,PC_GETCLINFO, PC_GETPARMS, or PC_SETPARMS. The real or effective ID of the calling process must match the real or effective ID of the affected processes, or must have superuser privilege. PC_GETCID This command takes the name field of a structure that contains a recognizable class name. The class ID and an array of class attribute data are returned. PC_GETCLINFO This command takes the ID field of a structure that contains a recognizable class identifier. The class name and an array of class attribute data are returned. PC_GETPARMS This command returns the scheduling class identifier or the class specific scheduling parameters of one of the specified processes.Even though idtype and id might specify a big set,PC_GETPARMS returns the parameter of only one process. The class selects the process. PC_SETPARMS This command sets the scheduling class or the class-specific scheduling parameters of the specified process or processes.