System information
Power Management 145
maximum CPU frequency the governor may select or to create a new governor. With
the -c option, you can also specify for which of the processors the settings should be
modified. That makes it easy to use a consistent policy across all processors without
adjusting the settings for each processor individually. For more details and the avail-
able options, refer to the cpupower-freqency-set man page or run cpupow-
erfrequency-set --help.
11.3.3 Monitoring Power Consumption
with powerTOP
Another useful tool for monitoring system power consumption is powerTOP. It
helps you to identify the reasons for unnecessary high power consumption (for ex-
ample, processes that are mainly responsible for waking up a processor from its
idle state) and to optimize your system settings to avoid these. It supports both In-
tel and AMD processors. The powertop package is available from the SUSE Lin-
ux Enterprise SDK. For information on how to access the SDK, refer to About This
Guide (pageix).
powerTOP combines various sources of information (analysis of programs, device
drivers, kernel options, amounts and sources of interrupts waking up processors from
sleep states) and shows them in one screen. Example11.5, “Example powerTOP
Output” (page145) shows which information categories are available:
Example11.5: Example powerTOP Output
Cn Avg residency P-states (frequencies)
C0 (cpu running) (11.6%) 2.00 Ghz 0.1%
polling 0.0ms ( 0.0%) 2.00 Ghz 0.0%
C1 4.4ms (57.3%) 1.87 Ghz 0.0%
C2 10.0ms (31.1%) 1064 Mhz 99.9%
Wakeups-from-idle per second : 11.2 interval: 5.0s
no ACPI power usage estimate available
Top causes for wakeups:
96.2% (826.0) <interrupt> : extra timer interrupt
0.9% ( 8.0) <kernel core> : usb_hcd_poll_rh_status (rh_timer_func)
0.3% ( 2.4) <interrupt> : megasas
0.2% ( 2.0) <kernel core> : clocksource_watchdog (clocksource_watchdog)
0.2% ( 1.6) <interrupt> : eth1-TxRx-0
0.1% ( 1.0) <interrupt> : eth1-TxRx-4