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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-

erfrequency-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 (pageix).

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. Example11.5, “Example powerTOP

Output” (page145) shows which information categories are available:

Example11.5: 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

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Red Hat ENTERPRISE LINUX 5.4 - SYSTEMTAP BEGINNERS GUIDE Informazioni Techniche Pagina 159