About Processes and System Performance

Some terms that are related to processes are:

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. An LWP contains information that is swappable and a kernel thread that contains information that has to be in memory all the time.

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 Oracle Solaris environment. Various process structures are as follows:

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 always be in main memory

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 3-1  Relationships Among 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.