Owner's manual

direct access to hardware and all memory. The OS switches application threads to privileged
mode to access operating system services.) This counter displays the average busy time as a
percentage of the sample time.
• % Privileged CPU Time—Percentage of non-idle processor time spent in privileged mode.
(Privileged mode is a processing mode designed for operating system components and
hardware-manipulating drivers. It allows direct access to hardware and all memory. The
alternative, user mode, is a restricted processing mode designed for applications, environment
subsystems, and integral subsystems. The operating system switches application threads to
privileged mode to access operating system services.) % Privileged CPU Time includes time
servicing interrupts and DPCs. A high rate of privileged time might be attributable to many
interrupts generated by a failing device. This counter displays the average busy time as a
percentage of the sample time.
• % DPC Time—Percentage of time that the processor spent receiving and servicing deferred
procedure calls (DPCs) during the sample interval. DPCs are interrupts that run at a lower
priority than standard interrupts. % DPC Time is a component of % Privileged Time because
DPCs are executed in privileged mode. They are counted separately and are not a component
of the interrupt counters. This counter displays the average busy time as a percentage of the
sample time.
• % Interrupt Time—Percentage of time the processor spent receiving and servicing hardware
interrupts during the sample interval. This value is an indirect indicator of the activity of devices
that generate interrupts, such as the system clock, the mouse, disk drivers, data communication
lines, network interface cards and other peripheral devices. These devices normally interrupt
the processor when they have completed a task or require attention. Normal thread execution
is suspended during interrupts. Most system clocks interrupt the processor every 10
milliseconds, creating a background of interrupt activity. This counter displays the average
busy time as a percentage of the sample time.
• % CPU Time (Thresholds Supported)—Percentage of time that the processor is executing a
non-idle thread. Designed as a primary indicator of processor activity, this counter is calculated
by measuring the time that the processor spends executing the thread of the idle process in
each sample interval, and subtracting that value from 100%. Each processor has an idle
thread that consumes cycles when no other threads are ready to run. It can be viewed as the
percentage of the sample interval spent doing useful work. This counter displays the average
percentage of busy time observed during the sample interval. It is calculated by monitoring
the time, the service was inactive, and then subtracting that value from 100%.
Server
System Health
• System Up Time—Elapsed time (in seconds) that the computer has been running since it was
last started. This counter displays the difference between the start time and the current time.
• Total Threads—Number of threads in the computer at the time of data collection. This count
is an instantaneous count, not an average over the time interval. A thread is the basic
executable entity that can execute instructions in a processor.
• Context Switches/sec—Combined rate at which all processors on the computer are switched
from one thread to another. Context switches occur when a running thread voluntarily
relinquishes the processor, is pre-empted by a higher priority ready thread, or switches between
user mode and privileged (kernel) mode to use an executive or subsystem service. The context
switches/sec rate for all threads running on all processors in the computer is measured in
numbers of switches. Context switch counters on the system and thread objects display the
difference between the values observed in the last two samples, divided by the duration of
the sample interval.
Sub-system Classification 119