NAME

       cpupower-set - Set processor power related kernel or hardware configurations

SYNOPSIS

       cpupower set [ -b VAL ]

DESCRIPTION

       cpupower set  sets kernel configurations or directly accesses hardware registers affecting
       processor power saving policies.

       Some options are platform wide, some affect single cores. By default values are applied on
       all  cores.  How  to  modify  single  core  configurations is described in the cpupower(1)
       manpage in the --cpu option section. Whether an option affects the whole system or can  be
       applied to individual cores is described in the Options sections.

       Use  cpupower  info   to  read  out current settings and whether they are supported on the
       system at all.

Options

       --perf-bias, -b
           Sets a register on supported Intel processore which  allows  software  to  convey  its
           policy  for  the  relative  importance  of  performance  versus  energy savings to the
           processor.

           The range of valid numbers is 0-15, where 0 is maximum performance and 15  is  maximum
           energy efficiency.

           The  processor uses this information in model-specific ways when it must select trade-
           offs between performance and energy efficiency.

           This policy hint does not supersede Processor Performance  states  (P-states)  or  CPU
           Idle  power  states  (C-states),  but allows software to have influence where it would
           otherwise be unable to express a preference.

           For example, this setting may tell the hardware how aggressively or conservatively  to
           control  frequency  in  the  "turbo  range" above the explicitly OS-controlled P-state
           frequency range.  It may also tell the hardware how aggressively it should  enter  the
           OS requested C-states.

           This option can be applied to individual cores only via the --cpu option, cpupower(1).

           Setting  the  performance bias value on one CPU can modify the setting on related CPUs
           as well (for example all CPUs on one socket), because of hardware  restrictions.   Use
           cpupower -c all info -b to verify.

           This options needs the msr kernel driver (CONFIG_X86_MSR) loaded.

SEE ALSO

       cpupower-info(1), cpupower-monitor(1), powertop(1)

AUTHORS

       --perf-bias parts written by Len Brown <len.brown@intel.com>
       Thomas Renninger <trenn@suse.de>

                                            22/02/2011                            CPUPOWER-SET(1)