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
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.
