Information Technology Reference
In-Depth Information
System Processes.
Displays the list of processes that were started by OS X (that is, the root user).
Other User Processes.
Displays the list of processes that are running under a username other than yours and
the root user.
Active Processes.
Displays just those processes that are currently using or have recently used the CPU.
Inactive Processes.
Displays just those processes that are running, but haven't used the CPU in a while.
Windowed Processes.
Displays just those processes associated with running programs that you can see in
the Dock (that is, the programs with open windows with which you can interact).
Selected Processes.
Displays specific processes. For example, if you want to watch certain processes, you'd
choose them and then choose Selected Processes.
Whichever processes you display, the list itself is divided into a number of columns that give you information
about the resources that each process is using. Here's a summary:
PID.
This column shows the process identifier, which is a unique numerical value that MacBook Air assigns
to the process while it's running.
Process Name.
This is the name (usually the executable filename) of the process. You also see the icon for
each windowed process.
User.
This value tells you the name of the user or service that launched the process.
You can control how often Activity Monitor refreshes its data. Choose View →Update Frequency, and then choose
Very Often (refreshes the data twice per second), Often (refreshes the data every second), Normally (refreshes the
data every 2 seconds — this is the default), or Less Often (refreshes the data every 5 seconds).
% CPU.
This is the key column for you in this section. The values here tell you the percentage of CPU re-
sources that each process is using. If your system seems sluggish, look for a process consuming all, or nearly
all, the CPU's resources. Most programs monopolize the CPU occasionally for short periods, but a program
stuck at 100 percent for a long time most likely has some kind of problem. In that case, try shutting down the
program or process, as described later in this chapter.
Threads.
This value tells you the number of threads that each process is using. A
thread
is a program task
that can run independently of, and usually concurrently with, other tasks in the same program, in which case the
program is said to support multithreading. Multithreading improves program performance, but programs that
have an unusually large number of threads can slow down the computer because they have to spend too much
time switching from one thread of execution to another.
Real Mem.
This value tells you approximately how much memory the process is using. This value is less
useful because a process might genuinely require a lot of memory to operate. However, if this value is steadily
increasing for a process that you're not using, it could indicate a problem, and you should shut down the pro-
cess, as described later in this chapter.
