Perfmon is TRWTF
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Trying to get an update to install on Win2012 R2 and it's taking ages so I fire up perfmon and go get a coffee.
Return later to see this;Bloody perfmon is taking all the CPU (149%, to be precise, which is another )
Kill perfmon and, right enough;
What's the sysops version of a Heisenbug?
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I typically use Process Explorer, because I don't really care for graphs that much. Speaking of graphs, it doesn't look like killing perfmon had much of an effect...
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Speaking of graphs, it doesn't look like killing perfmon had much of an effect...
It did. The CPU had been on the roof and I killed perfmon halfway through that graph's timeline, at which point the spikiness that I'd expect to be Windows Update got going.
...and the thermometer / progress bar on the update window started moving!
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That's not perfmon, it's resource monitor - which is a whole different beast altogether. Perfmon is just a bunch of counters and numbers (that applications submit to the OS anyway), resourcemon is more intensive.
Nevertheless, it shouldn't be such a resource hog.
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t'was "perfmon.exe" that was eating the cpu...
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Oh. Oops, I missed that...
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149%, to be precise, which is another
This has been topic of dispute in our office in the past. There are two ways to measure CPU usage: As a percentage of a single core, or as a percentage of all cores. When looking at processes or especially threads calculating a percentage of a single core makes more sense. Otherwise a single-threaded process on a 48-core machine would never use more than 2% of CPU, but its CPU load could still be the bottleneck.
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t'was "perfmon.exe" that was eating the cpu...
Isn't that how you measure CPU load? Create a low-priority thread that never blocks on every core. Then compare its CPU load with the theoretical maximum for all the cores.