System Administration Guide, Volume 2

Processes and System Performance

Terms related to processes are described in the table below.

Table 34-1 Process Terminology


Term	Description
Process	An instance of program in execution.
Lightweight process (LWP)	Is a virtual CPU or execution resource. LWPs are scheduled by the kernel to use available CPU resources based on their scheduling class and priority. LWPs include a kernel thread, which contains information that has to be in memory all the time and an LWP, which contains information that is swappable.
Application thread	A series of instructions with a separate stack that can execute independently in a user's address space. They can be multiplexed on top of LWPs.

A process can consist of multiple LWPs and multiple application threads. The kernel schedules a kernel-thread structure, which is the scheduling entity in the SunOS environment. Various process structures are described in the table below.

Table 34-2 Process Structures


Structure	Description
`proc`	Contains information that pertains to the whole process and has to be in main memory all the time.
`kthread`	Contains information that pertains to one LWP and has to be in main memory all the time.
`user`	Contains the per process information that is swappable.
`klwp`	Contains the per LWP process information that is swappable.

The figure below illustrates the relationship of these structures.

Figure 34-1 Process Structures

Most process resources are accessible to all the threads in the process. Almost all process virtual memory is shared. A change in shared data by one thread is available to the other threads in the process.

Commands for Managing Processes

The table below describes commands for managing processes.

Table 34-3 Commands for Managing Processes


Use This Command ...	To ...
ps(1), pgrep(1), and prstat(1M)	Check the status of active processes on a system, as well as display detailed information about the processes
dispadmin(1M)	List default scheduling policies
priocntl(1)	Assign processes to a priority class and manage process priorities
nice(1)	Change the priority of a timesharing process

Another feature enables the control of process groups over processor sets. Using processor sets means process groups can bind to a group of processors rather than to just a single processor. The /usr/sbin/psrset command gives a system administrator control over the creation and management of processor sets. See psrset(1M) for more information.

See Chapter 35, Managing Processes (Tasks) for more information about commands for managing processes.