X86_ENERGY_PERF_POLICY(8) System Manager's Manual X86_ENERGY_PERF_POLICY(8)NAME
x86_energy_perf_policy - read or write MSR_IA32_ENERGY_PERF_BIAS
SYNOPSIS
x86_energy_perf_policy [-c cpu] [-v] -r
x86_energy_perf_policy [-c cpu] [-v] 'performance'
x86_energy_perf_policy [-c cpu] [-v] 'normal'
x86_energy_perf_policy [-c cpu] [-v] 'powersave'
x86_energy_perf_policy [-c cpu] [-v] n
DESCRIPTION
x86_energy_perf_policy allows software to convey its policy for the relative importance of performance versus energy savings to the proces-
sor.
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 is should enter the OS requested C-
states.
Support for this feature is indicated by CPUID.06H.ECX.bit3 per the Intel Architectures Software Developer's Manual.
Options
-c limits operation to a single CPU. The default is to operate on all CPUs. Note that MSR_IA32_ENERGY_PERF_BIAS is defined per logical
processor, but that the initial implementations of the MSR were shared among all processors in each package.
-v increases verbosity. By default x86_energy_perf_policy is silent.
-r is for "read-only" mode - the unchanged state is read and displayed.
performance Set a policy where performance is paramount. The processor will be unwilling to sacrifice any performance for the sake of
energy saving. This is the hardware default.
normal Set a policy with a normal balance between performance and energy efficiency. The processor will tolerate minor performance compro-
mise for potentially significant energy savings. This reasonable default for most desktops and servers.
powersave Set a policy where the processor can accept a measurable performance hit to maximize energy efficiency.
n Set MSR_IA32_ENERGY_PERF_BIAS to the specified number. The range of valid numbers is 0-15, where 0 is maximum performance and 15 is max-
imum energy efficiency.
NOTES
x86_energy_perf_policy runs only as root.
FILES
/dev/cpu/*/msr
SEE ALSO msr(4)AUTHORS
Written by Len Brown <len.brown@intel.com>
X86_ENERGY_PERF_POLICY(8)
Check Out this Related Man Page
assign_cpu_to_pset(3) Library Functions Manual assign_cpu_to_pset(3)NAME
assign_cpu_to_pset - Assigns a processor to a processor set
LIBRARY
Pset Library (libpset.a)
Mach Library (libmach.a)
SYNOPSIS
#include <sys/types.h> #include <sys/processor.h>
int assign_cpu_to_pset(
unsigned long cpu,
long pset_id ,
long option );
PARAMETERS
Processor or processors to assign to the specified processor set. Processor set identifier, which is returned by the create_pset function.
Specifies a bit mask. Currently, only the ANY_CPU bit is supported. If this bit is set, the value specified by the cpu variable is the
number of processors to be assigned to the specified processor set from the default processor set. If the ANY_CPU bit is not set, the
value specified by the cpu variable is the mask of processors to be assigned to the processor set.
DESCRIPTION
The assign_cpu_to_pset function removes processors from their current processor set and assigns them to the processor set specified by the
pset_id variable. This function requires root privileges.
If the ANY_CPU option is specified, the number of processors specified by the cpu variable are assigned from the default processor set to
the processor set that is specified with the pset_id variable. If the specified number of processors are not available in the default pro-
cessor set, an error is returned and no processors are assigned.
If the ANY_CPU option is not set, the value specified by the cpu variable is a mask of processors to be assigned to the specified processor
set. For example, if you specify a cpu value of 6, then processors 2 and 3 are assigned to the processor set.
Note that processors are not required to start in slot 0 on some platforms. For example, you may see a three-processor system with proces-
sors in slots 6, 7, and 8. The console assigns the master processor at power up, which is usually the processor in slot 0 if it is occu-
pied. However, there is no requirement that slot 0 must be populated or that the master is the first processor on the bus. In the example
of the three-processor (slots 6, 7, and 8) system, the master processor will be the one in slot 6.
Processor assignments are logged in the /var/adm/wtmp file.
RETURN VALUES
If the processor assignment is successful, the assign_cpu_to_pset function returns zero (0). If the assignment is unsuccessful, the func-
tion returns a negative number. Use the print_pset_error function to print a message that describes the error.
FILES
/var/adm/wtmp
RELATED INFORMATION bind_to_cpu(3), create_pset(3), destroy_pset(3), assign_pid_to_pset(3), print_pset_error(3), processor_sets(4), pset_create(1) delim off
assign_cpu_to_pset(3)