Page 80 - DCAP103_Principle of operating system

Unit 3: Process Management-II

Notes
We can view context switch data in two ways:

• The System\Context Switches/sec counter in System Monitor reports systemwide context
switches.

• The Thread (_Total)\Context Switches/sec counter reports the total number of context
switches generated per second by all threads.

Although these counters might vary slightly due to sampling, generally they will be nearly equal.

Figure 3.6: System Wide Context Switches During a Processor Bottleneck

In Figure 3.6, Processor (_Total)\% Processor Time jumps to about 60 per cent during the
sample interval. System\Processor Queue Length (scaled by a factor of 10), shows that
the queue varies from 2 to 6, with a mean near 4. System\Context Switches (shown scaled
by a factor of 10), reveals an average of about 750 switches per second. A rate of context
switches from 500 to 2,000 per second might indicate a problem with a network adapter or
a device driver or that you are using an inefficient server-based application that spawns
too many threads.
The Pviewer utility on the on the Windows 2000 operating system CD reports context switch
data. For information about installing and using the Windows 2000 Support Tools and
Support Tools Help, see the file Sreadme.doc in the \Support\Tools folder of the Windows
2000 operating system CD.

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