System information
138 System Analysis and Tuning Guide
However, using this governor often does not lead to the expected power savings
as the highest savings can usually be achieved at idle through entering C-states.
Due to running processes at the lowest frequency with the powersave governor,
processes will take longer to finish, thus prolonging the time for the system to en-
ter any idle C-states.
Tuning options: The range of minimum frequencies available to the governor can
be adjusted (for example, with the cpupower command line tool).
On-demand Governor
The kernel implementation of a dynamic CPU frequency policy: The governor
monitors the processor utilization. As soon as it exceeds a certain threshold, the
governor will set the frequency to the highest available. If the utilization is less
than the threshold, the next lowest frequency is used. If the system continues to
be underemployed, the frequency is again reduced until the lowest available fre-
quency is set.
For SUSE Linux Enterprise, the on-demand governor is the default governor and
the one that has the best test coverage.
Tuning options: The range of available frequencies, the rate at which the gov-
ernor checks utilization, and the utilization threshold can be adjusted. An-
other parameter you might want to change for the on-demand governor is
ignore_nice_load. For details, refer to Procedure11.1, “Ignoring Nice Val-
ues in Processor Utilization” (page147).
Conservative Governor
Similar to the on-demand implementation, this governor also dynamically ad-
justs frequencies based on processor utilization, except that it allows for a more
gradual increase in power. If processor utilization exceeds a certain threshold, the
governor does not immediately switch to the highest available frequency (as the
on-demand governor does), but only to next higher frequency available.
Tuning options: The range of available frequencies, the rate at which the gover-
nor checks utilization, the utilization thresholds, and the frequency step rate can
be adjusted.
11.2.2 Related Files and Directories
If the CPUfreq subsystem in enabled on your system (which it is by default with
SUSE Linux Enterprise Server), you can find the relevant files and directories under