Processes and System Performance

The following table describes terms that are related to processes.

Table 11-1 Process Terminology

Term	Description
Process	Any system activity or job. Each time you boot a system, execute a command, or start an application, the system activates one or more processes.
Lightweight process (LWP)	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 and an LWP. A kernel thread contains information that has to be in memory all the time. An LWP 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. Application threads 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 following table.

Table 11-2 Process Structures

Structure	Description
`proc`	Contains information that pertains to the whole process and must be in main memory all the time
`kthread`	Contains information that pertains to one LWP and must 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 following figure illustrates the relationships among these process structures.

Figure 11-1 Relationships Among Process Structures

image:The preceding text in the table describes the graphic.

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.

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