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diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 new file mode 100644 index 000000000..78c636189 --- /dev/null +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 @@ -0,0 +1,213 @@ +.\" This page Copyright (C) 2010 - 2015 Len Brown <len.brown@intel.com> +.\" Distributed under the GPL, Copyleft 1994. +.TH X86_ENERGY_PERF_POLICY 8 +.SH NAME +x86_energy_perf_policy \- Manage Energy vs. Performance Policy via x86 Model Specific Registers +.SH SYNOPSIS +.B x86_energy_perf_policy +.RB "[ options ] [ scope ] [field \ value]" +.br +.RB "scope: \-\-cpu\ cpu-list | \-\-pkg\ pkg-list" +.br +.RB "cpu-list, pkg-list: # | #,# | #-# | all" +.br +.RB "field: \-\-all | \-\-epb | \-\-hwp-epp | \-\-hwp-min | \-\-hwp-max | \-\-hwp-desired" +.br +.RB "other: (\-\-force | \-\-hwp-enable | \-\-turbo-enable) value)" +.br +.RB "value: # | default | performance | balance-performance | balance-power | power" +.SH DESCRIPTION +\fBx86_energy_perf_policy\fP +displays and updates energy-performance policy settings specific to +Intel Architecture Processors. Settings are accessed via Model Specific Register (MSR) +updates, no matter if the Linux cpufreq sub-system is enabled or not. + +Policy in MSR_IA32_ENERGY_PERF_BIAS (EPB) +may affect a wide range of hardware decisions, +such as how aggressively the hardware enters and exits CPU idle states (C-states) +and Processor Performance States (P-states). +This policy hint does not replace explicit OS C-state and P-state selection. +Rather, it tells the hardware how aggressively to implement those selections. +Further, it allows the OS to influence energy/performance trade-offs where there +is no software interface, such as in the opportunistic "turbo-mode" P-state range. +Note that MSR_IA32_ENERGY_PERF_BIAS is defined per CPU, +but some implementations +share a single MSR among all CPUs in each processor package. +On those systems, a write to EPB on one processor will +be visible, and will have an effect, on all CPUs +in the same processor package. + +Hardware P-States (HWP) are effectively an expansion of hardware +P-state control from the opportunistic turbo-mode P-state range +to include the entire range of available P-states. +On Broadwell Xeon, the initial HWP implementation, EPB influenced HWP. +That influence was removed in subsequent generations, +where it was moved to the +Energy_Performance_Preference (EPP) field in +a pair of dedicated MSRs -- MSR_IA32_HWP_REQUEST and MSR_IA32_HWP_REQUEST_PKG. + +EPP is the most commonly managed knob in HWP mode, +but MSR_IA32_HWP_REQUEST also allows the user to specify +minimum-frequency for Quality-of-Service, +and maximum-frequency for power-capping. +MSR_IA32_HWP_REQUEST is defined per-CPU. + +MSR_IA32_HWP_REQUEST_PKG has the same capability as MSR_IA32_HWP_REQUEST, +but it can simultaneously set the default policy for all CPUs within a package. +A bit in per-CPU MSR_IA32_HWP_REQUEST indicates whether it is +over-ruled-by or exempt-from MSR_IA32_HWP_REQUEST_PKG. + +MSR_HWP_CAPABILITIES shows the default values for the fields +in MSR_IA32_HWP_REQUEST. It is displayed when no values +are being written. + +.SS SCOPE OPTIONS +.PP +\fB-c, --cpu\fP Operate on the MSR_IA32_HWP_REQUEST for each CPU in a CPU-list. +The CPU-list may be comma-separated CPU numbers, with dash for range +or the string "all". Eg. '--cpu 1,4,6-8' or '--cpu all'. +When --cpu is used, \fB--hwp-use-pkg\fP is available, which specifies whether the per-cpu +MSR_IA32_HWP_REQUEST should be over-ruled by MSR_IA32_HWP_REQUEST_PKG (1), +or exempt from MSR_IA32_HWP_REQUEST_PKG (0). + +\fB-p, --pkg\fP Operate on the MSR_IA32_HWP_REQUEST_PKG for each package in the package-list. +The list is a string of individual package numbers separated +by commas, and or ranges of package numbers separated by a dash, +or the string "all". +For example '--pkg 1,3' or '--pkg all' + +.SS VALUE OPTIONS +.PP +.I normal | default +Set a policy with a normal balance between performance and energy efficiency. +The processor will tolerate minor performance compromise +for potentially significant energy savings. +This is a reasonable default for most desktops and servers. +"default" is a synonym for "normal". +.PP +.I performance +Set a policy for maximum performance, +accepting no performance sacrifice for the benefit of energy efficiency. +.PP +.I balance-performance +Set a policy with a high priority on performance, +but allowing some performance loss to benefit energy efficiency. +.PP +.I balance-power +Set a policy where the performance and power are balanced. +This is the default. +.PP +.I power +Set a policy where the processor can accept +a measurable performance impact to maximize energy efficiency. + +.PP +The following table shows the mapping from the value strings above to actual MSR values. +This mapping is defined in the Linux-kernel header, msr-index.h. + +.nf +VALUE STRING EPB EPP +performance 0 0 +balance-performance 4 128 +normal, default 6 128 +balance-power 8 192 +power 15 255 +.fi +.PP +For MSR_IA32_HWP_REQUEST performance fields +(--hwp-min, --hwp-max, --hwp-desired), the value option +is in units of 100 MHz, Eg. 12 signifies 1200 MHz. + +.SS FIELD OPTIONS +\fB-a, --all value-string\fP Sets all EPB and EPP and HWP limit fields to the value associated with +the value-string. In addition, enables turbo-mode and HWP-mode, if they were previous disabled. +Thus "--all normal" will set a system without cpufreq into a well known configuration. +.PP +\fB-B, --epb\fP set EPB per-core or per-package. +See value strings in the table above. +.PP +\fB-d, --debug\fP debug increases verbosity. By default +x86_energy_perf_policy is silent for updates, +and verbose for read-only mode. +.PP +\fB-P, --hwp-epp\fP set HWP.EPP per-core or per-package. +See value strings in the table above. +.PP +\fB-m, --hwp-min\fP request HWP to not go below the specified core/bus ratio. +The "default" is the value found in IA32_HWP_CAPABILITIES.min. +.PP +\fB-M, --hwp-max\fP request HWP not exceed a the specified core/bus ratio. +The "default" is the value found in IA32_HWP_CAPABILITIES.max. +.PP +\fB-D, --hwp-desired\fP request HWP 'desired' frequency. +The "normal" setting is 0, which +corresponds to 'full autonomous' HWP control. +Non-zero performance values request a specific performance +level on this processor, specified in multiples of 100 MHz. +.PP +\fB-w, --hwp-window\fP specify integer number of microsec +in the sliding window that HWP uses to maintain average frequency. +This parameter is meaningful only when the "desired" field above is non-zero. +Default is 0, allowing the HW to choose. +.SH OTHER OPTIONS +.PP +\fB-f, --force\fP writes the specified values without bounds checking. +.PP +\fB-U, --hwp-use-pkg\fP (0 | 1), when used in conjunction with --cpu, +indicates whether the per-CPU MSR_IA32_HWP_REQUEST should be overruled (1) +or exempt (0) from per-Package MSR_IA32_HWP_REQUEST_PKG settings. +The default is exempt. +.PP +\fB-H, --hwp-enable\fP enable HardWare-P-state (HWP) mode. Once enabled, system RESET is required to disable HWP mode. +.PP +\fB-t, --turbo-enable\fP enable (1) or disable (0) turbo mode. +.PP +\fB-v, --version\fP print version and exit. +.PP +If no request to change policy is made, +the default behavior is to read +and display the current system state, +including the default capabilities. +.SH WARNING +.PP +This utility writes directly to Model Specific Registers. +There is no locking or coordination should this utility +be used to modify HWP limit fields at the same time that +intel_pstate's sysfs attributes access the same MSRs. +.PP +Note that --hwp-desired and --hwp-window are considered experimental. +Future versions of Linux reserve the right to access these +fields internally -- potentially conflicting with user-space access. +.SH EXAMPLE +.nf +# sudo x86_energy_perf_policy +cpu0: EPB 6 +cpu0: HWP_REQ: min 6 max 35 des 0 epp 128 window 0x0 (0*10^0us) use_pkg 0 +cpu0: HWP_CAP: low 1 eff 8 guar 27 high 35 +cpu1: EPB 6 +cpu1: HWP_REQ: min 6 max 35 des 0 epp 128 window 0x0 (0*10^0us) use_pkg 0 +cpu1: HWP_CAP: low 1 eff 8 guar 27 high 35 +cpu2: EPB 6 +cpu2: HWP_REQ: min 6 max 35 des 0 epp 128 window 0x0 (0*10^0us) use_pkg 0 +cpu2: HWP_CAP: low 1 eff 8 guar 27 high 35 +cpu3: EPB 6 +cpu3: HWP_REQ: min 6 max 35 des 0 epp 128 window 0x0 (0*10^0us) use_pkg 0 +cpu3: HWP_CAP: low 1 eff 8 guar 27 high 35 +.fi +.SH NOTES +.B "x86_energy_perf_policy" +runs only as root. +.SH FILES +.ta +.nf +/dev/cpu/*/msr +.fi +.SH "SEE ALSO" +.nf +msr(4) +Intel(R) 64 and IA-32 Architectures Software Developer's Manual +.fi +.PP +.SH AUTHORS +.nf +Len Brown |