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If an MSR based monitor is run in parallel this is not needed. This is the default case on all/most Intel machines. But when only sysfs info is read via cpupower monitor -m Idle_Stats (typically the case for non root users) or when other monitors are PCI based (AMD), Idle_Stats, read from sysfs can be totally bogus: cpupower monitor -m Idle_Stats PKG |CORE|CPU | POLL | C1-N | C3-N | C6-N 0| 0| 0| 0.00| 0.00| 0.24| 99.81 0| 0| 32| 0.00| 0.00| 0.00| 100.7 ... 0| 17| 20| 0.00| 0.00| 0.00| 173.1 0| 17| 52| 0.00| 0.00| 0.07| 173.0 0| 18| 68| 0.00| 0.00| 0.00| 0.00 0| 18| 76| 0.00| 0.00| 0.00| 0.00 ... With the -c option all cores are woken up and the kernel did update cpuidle statistics before reading out sysfs. This causes some overhead. Therefore avoid if possible, use if needed: cpupower monitor -c -m Idle_Stats PKG |CORE|CPU | POLL | C1-N | C3-N | C6-N 0| 0| 0| 0.00| 0.00| 0.00| 100.2 0| 0| 32| 0.00| 0.00| 0.00| 100.2 ... 0| 8| 8| 0.00| 0.00| 0.00| 99.82 0| 8| 40| 0.00| 0.00| 0.00| 99.81 0| 9| 24| 0.00| 0.00| 0.00| 100.3 0| 9| 56| 0.00| 0.00| 0.00| 100.2 0| 16| 4| 0.00| 0.00| 0.00| 99.75 0| 16| 36| 0.00| 0.00| 0.00| 99.38 ... Signed-off-by: Thomas Renninger <trenn@suse.de> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
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