Performance Monitor Reports Inconsistent Data About CPU Usage (810876)
The information in this article applies to:
- Microsoft Windows 2000 Advanced Server
- Microsoft Windows 2000 Professional
- Microsoft Windows 2000 Server
- Microsoft Windows XP Home Edition
- Microsoft Windows XP Professional
SYMPTOMSPerformance Monitor may record CPU usage that
is inconsistent with the computer activities during the sampling period on
some single or multiprocessor computers. It may also report high and low CPU
usage cycles when there is consistent network and system load. The cycles may
vary from 2 to 30 minutes of high or low CPU usage.STATUS Microsoft
has confirmed that this is a problem in the Microsoft products that are listed
at the beginning of this article.
MORE INFORMATIONPerformance Monitor uses periodic sampling to determine CPU
usage (that is, idle time or privileged time). If the activity on the computer
synchronizes with the sampling interrupt, Performance Monitor may report the
system CPU usage inaccurately. For example, if the activity on the
computer occurs every 10 milliseconds (ms), Performance Monitor may report the
CPU as very active if the activity occurs every time it interrupts and samples
the CPU usage. If the activity occurs out of phase, Performance Monitor reports
very low CPU usage.
Sometimes such activities may be in phase with the sampling
interrupt, but then they slowly drift out of phase, especially when external timers drive
such activities. For example, in a client server program scenario, if
the client sends a packet to the server in a loop and then sleeps for 1 millisecond between the
packets, the sleep(1) on the client (whose clock may drift slightly as compared to
the clock on the server computer) may cause the Performance Monitor to report
alternating high and low CPU usage cycles on server.
| Modification Type: | Major | Last Reviewed: | 6/5/2003 |
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| Keywords: | kbprb KB810876 |
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