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Title
CPU Metrics are showing negative numbers -
Description
Seeing intermittent negative values in CPU metrics - both totals in SQL Server Activity CPU history and in Windows CPU details by logical processor. After reviewing KB97245, restarted the Diagnostic Server, but negative metrics still show up. -
Resolution
Spotlight shows CPU drilldown the CPU Interrupts are derived from the below Microsoft WMI query.
wmic path Win32_PerfRawData_PerfOS_Processor get InterruptsPerSec, Name, PercentInterruptTime, PercentPrivilegedTime, PercentUserTime, PercentIdleTime
More details info from Microsoft link:
http://msdn.microsoft.com/en-us/library/windows/desktop/aa394317%28v=vs.85%29.aspxNeed to run the query twice, find the difference between the InterruptsPerSec field and divide by the number of seconds between two samples to get the figure shown. (Giving the “rate”)
The “Total” figure shown on the SQL Activity | CPU Utilization graph comes from the same query as above.
TotalPct = (InterruptPct+KernelPct+UserPct)/(100-VMWaitPct)*100
Where...
InterruptPct = rate derived from InterruptsPerSec column / 10000
KernelPct = rate derived from PercentPrivilegedTime column / 100000
UserPct = rate derived from the PercentUserTime column / 100000
VMWaitPct = 100-InterruptPct-KernelPct-UserPct-IdlePct (or 0 in a non-virtualised environment)