Perfmon is TRWTF



  • 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 undefined)

    Kill perfmon and, right enough;

    What's the sysops version of a Heisenbug?



  • 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...



  • @LB_ said:

    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!



  • 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.



  • t'was "perfmon.exe" that was eating the cpu...



  • Oh. Oops, I missed that...



  • @skotl said:

    149%, to be precise, which is another undefined

    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.



  • @skotl said:

    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. undefined


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