tools: create power/x86/x86_energy_perf_policy
MSR_IA32_ENERGY_PERF_BIAS first became available on Westmere Xeon. It is implemented in all Sandy Bridge processors -- mobile, desktop and server. It is expected to become increasingly important in subsequent generations. x86_energy_perf_policy is a user-space utility to set the hardware energy vs performance policy hint in the processor. Most systems would benefit from "x86_energy_perf_policy normal" at system startup, as the hardware default is maximum performance at the expense of energy efficiency. See x86_energy_perf_policy.8 man page for more information. Background: Linux-2.6.36 added "epb" to /proc/cpuinfo to indicate if an x86 processor supports MSR_IA32_ENERGY_PERF_BIAS, without actually modifying the MSR. In March, 2010, Venkatesh Pallipadi proposed a small driver that programmed MSR_IA32_ENERGY_PERF_BIAS, based on the cpufreq governor in use. It also offered a boot-time cmdline option to override. http://lkml.org/lkml/2010/3/4/457 But hiding the hardware policy behind the governor choice was deemed "kinda icky". In June, 2010, I proposed a generic user/kernel API to generalize the power/performance policy trade-off. "RFC: /sys/power/policy_preference" http://lkml.org/lkml/2010/6/16/399 That is my preference for implementing this capability, but I received no support on the list. So in September, 2010, I sent x86_energy_perf_policy.c to LKML, a user-space utility that scribbles directly to the MSR. http://lkml.org/lkml/2010/9/28/246 Here is that same utility, after responding to some review feedback, to live in tools/power/, where it is easily found. Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Len Brown
Родитель
f6f94e2ab1
Коммит
d5532ee7b4
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@ -0,0 +1,8 @@
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x86_energy_perf_policy : x86_energy_perf_policy.c
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clean :
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rm -f x86_energy_perf_policy
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install :
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install x86_energy_perf_policy /usr/bin/
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install x86_energy_perf_policy.8 /usr/share/man/man8/
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@ -0,0 +1,104 @@
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.\" This page Copyright (C) 2010 Len Brown <len.brown@intel.com>
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.\" Distributed under the GPL, Copyleft 1994.
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.TH X86_ENERGY_PERF_POLICY 8
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.SH NAME
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x86_energy_perf_policy \- read or write MSR_IA32_ENERGY_PERF_BIAS
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.SH SYNOPSIS
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.ft B
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.B x86_energy_perf_policy
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.RB [ "\-c cpu" ]
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.RB [ "\-v" ]
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.RB "\-r"
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.br
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.B x86_energy_perf_policy
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.RB [ "\-c cpu" ]
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.RB [ "\-v" ]
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.RB 'performance'
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.br
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.B x86_energy_perf_policy
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.RB [ "\-c cpu" ]
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.RB [ "\-v" ]
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.RB 'normal'
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.br
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.B x86_energy_perf_policy
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.RB [ "\-c cpu" ]
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.RB [ "\-v" ]
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.RB 'powersave'
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.br
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.B x86_energy_perf_policy
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.RB [ "\-c cpu" ]
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.RB [ "\-v" ]
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.RB n
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.br
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.SH DESCRIPTION
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\fBx86_energy_perf_policy\fP
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allows software to convey
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its policy for the relative importance of performance
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versus energy savings to the processor.
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The processor uses this information in model-specific ways
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when it must select trade-offs between performance and
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energy efficiency.
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This policy hint does not supersede Processor Performance states
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(P-states) or CPU Idle power states (C-states), but allows
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software to have influence where it would otherwise be unable
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to express a preference.
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For example, this setting may tell the hardware how
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aggressively or conservatively to control frequency
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in the "turbo range" above the explicitly OS-controlled
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P-state frequency range. It may also tell the hardware
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how aggressively is should enter the OS requested C-states.
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Support for this feature is indicated by CPUID.06H.ECX.bit3
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per the Intel Architectures Software Developer's Manual.
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.SS Options
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\fB-c\fP limits operation to a single CPU.
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The default is to operate on all CPUs.
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Note that MSR_IA32_ENERGY_PERF_BIAS is defined per
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logical processor, but that the initial implementations
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of the MSR were shared among all processors in each package.
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.PP
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\fB-v\fP increases verbosity. By default
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x86_energy_perf_policy is silent.
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.PP
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\fB-r\fP is for "read-only" mode - the unchanged state
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is read and displayed.
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.PP
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.I performance
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Set a policy where performance is paramount.
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The processor will be unwilling to sacrifice any performance
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for the sake of energy saving. This is the hardware default.
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.PP
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.I normal
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Set a policy with a normal balance between performance and energy efficiency.
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The processor will tolerate minor performance compromise
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for potentially significant energy savings.
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This reasonable default for most desktops and servers.
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.PP
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.I powersave
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Set a policy where the processor can accept
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a measurable performance hit to maximize energy efficiency.
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.PP
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.I n
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Set MSR_IA32_ENERGY_PERF_BIAS to the specified number.
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The range of valid numbers is 0-15, where 0 is maximum
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performance and 15 is maximum energy efficiency.
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.SH NOTES
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.B "x86_energy_perf_policy "
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runs only as root.
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.SH FILES
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.ta
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.nf
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/dev/cpu/*/msr
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.fi
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.SH "SEE ALSO"
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msr(4)
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.PP
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.SH AUTHORS
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.nf
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Written by Len Brown <len.brown@intel.com>
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@ -0,0 +1,325 @@
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/*
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* x86_energy_perf_policy -- set the energy versus performance
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* policy preference bias on recent X86 processors.
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*/
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/*
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* Copyright (c) 2010, Intel Corporation.
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* Len Brown <len.brown@intel.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/resource.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <sys/time.h>
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#include <stdlib.h>
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#include <string.h>
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unsigned int verbose; /* set with -v */
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unsigned int read_only; /* set with -r */
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char *progname;
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unsigned long long new_bias;
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int cpu = -1;
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/*
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* Usage:
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*
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* -c cpu: limit action to a single CPU (default is all CPUs)
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* -v: verbose output (can invoke more than once)
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* -r: read-only, don't change any settings
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*
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* performance
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* Performance is paramount.
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* Unwilling to sacrafice any performance
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* for the sake of energy saving. (hardware default)
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*
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* normal
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* Can tolerate minor performance compromise
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* for potentially significant energy savings.
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* (reasonable default for most desktops and servers)
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*
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* powersave
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* Can tolerate significant performance hit
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* to maximize energy savings.
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*
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* n
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* a numerical value to write to the underlying MSR.
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*/
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void usage(void)
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{
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printf("%s: [-c cpu] [-v] "
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"(-r | 'performance' | 'normal' | 'powersave' | n)\n",
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progname);
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exit(1);
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}
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#define MSR_IA32_ENERGY_PERF_BIAS 0x000001b0
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#define BIAS_PERFORMANCE 0
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#define BIAS_BALANCE 6
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#define BIAS_POWERSAVE 15
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void cmdline(int argc, char **argv)
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{
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int opt;
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progname = argv[0];
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while ((opt = getopt(argc, argv, "+rvc:")) != -1) {
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switch (opt) {
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case 'c':
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cpu = atoi(optarg);
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break;
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case 'r':
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read_only = 1;
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break;
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case 'v':
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verbose++;
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break;
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default:
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usage();
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}
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}
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/* if -r, then should be no additional optind */
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if (read_only && (argc > optind))
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usage();
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/*
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* if no -r , then must be one additional optind
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*/
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if (!read_only) {
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if (argc != optind + 1) {
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printf("must supply -r or policy param\n");
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usage();
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}
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if (!strcmp("performance", argv[optind])) {
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new_bias = BIAS_PERFORMANCE;
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} else if (!strcmp("normal", argv[optind])) {
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new_bias = BIAS_BALANCE;
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} else if (!strcmp("powersave", argv[optind])) {
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new_bias = BIAS_POWERSAVE;
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} else {
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char *endptr;
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new_bias = strtoull(argv[optind], &endptr, 0);
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if (endptr == argv[optind] ||
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new_bias > BIAS_POWERSAVE) {
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fprintf(stderr, "invalid value: %s\n",
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argv[optind]);
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usage();
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}
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}
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}
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}
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/*
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* validate_cpuid()
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* returns on success, quietly exits on failure (make verbose with -v)
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*/
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void validate_cpuid(void)
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{
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unsigned int eax, ebx, ecx, edx, max_level;
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char brand[16];
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unsigned int fms, family, model, stepping;
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eax = ebx = ecx = edx = 0;
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asm("cpuid" : "=a" (max_level), "=b" (ebx), "=c" (ecx),
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"=d" (edx) : "a" (0));
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if (ebx != 0x756e6547 || edx != 0x49656e69 || ecx != 0x6c65746e) {
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if (verbose)
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fprintf(stderr, "%.4s%.4s%.4s != GenuineIntel",
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(char *)&ebx, (char *)&edx, (char *)&ecx);
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exit(1);
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}
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asm("cpuid" : "=a" (fms), "=c" (ecx), "=d" (edx) : "a" (1) : "ebx");
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family = (fms >> 8) & 0xf;
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model = (fms >> 4) & 0xf;
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stepping = fms & 0xf;
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if (family == 6 || family == 0xf)
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model += ((fms >> 16) & 0xf) << 4;
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if (verbose > 1)
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printf("CPUID %s %d levels family:model:stepping "
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"0x%x:%x:%x (%d:%d:%d)\n", brand, max_level,
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family, model, stepping, family, model, stepping);
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if (!(edx & (1 << 5))) {
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if (verbose)
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printf("CPUID: no MSR\n");
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exit(1);
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}
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/*
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* Support for MSR_IA32_ENERGY_PERF_BIAS
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* is indicated by CPUID.06H.ECX.bit3
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*/
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asm("cpuid" : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (6));
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if (verbose)
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printf("CPUID.06H.ECX: 0x%x\n", ecx);
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if (!(ecx & (1 << 3))) {
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if (verbose)
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printf("CPUID: No MSR_IA32_ENERGY_PERF_BIAS\n");
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exit(1);
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}
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return; /* success */
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}
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unsigned long long get_msr(int cpu, int offset)
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{
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unsigned long long msr;
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char msr_path[32];
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int retval;
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int fd;
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sprintf(msr_path, "/dev/cpu/%d/msr", cpu);
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fd = open(msr_path, O_RDONLY);
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if (fd < 0) {
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printf("Try \"# modprobe msr\"\n");
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perror(msr_path);
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exit(1);
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}
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retval = pread(fd, &msr, sizeof msr, offset);
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if (retval != sizeof msr) {
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printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval);
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exit(-2);
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}
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close(fd);
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return msr;
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}
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unsigned long long put_msr(int cpu, unsigned long long new_msr, int offset)
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{
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unsigned long long old_msr;
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char msr_path[32];
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int retval;
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int fd;
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sprintf(msr_path, "/dev/cpu/%d/msr", cpu);
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fd = open(msr_path, O_RDWR);
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if (fd < 0) {
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perror(msr_path);
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exit(1);
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}
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retval = pread(fd, &old_msr, sizeof old_msr, offset);
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if (retval != sizeof old_msr) {
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perror("pwrite");
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printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval);
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exit(-2);
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}
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retval = pwrite(fd, &new_msr, sizeof new_msr, offset);
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if (retval != sizeof new_msr) {
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perror("pwrite");
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printf("pwrite cpu%d 0x%x = %d\n", cpu, offset, retval);
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exit(-2);
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}
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close(fd);
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return old_msr;
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}
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void print_msr(int cpu)
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{
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printf("cpu%d: 0x%016llx\n",
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cpu, get_msr(cpu, MSR_IA32_ENERGY_PERF_BIAS));
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}
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void update_msr(int cpu)
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{
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unsigned long long previous_msr;
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previous_msr = put_msr(cpu, new_bias, MSR_IA32_ENERGY_PERF_BIAS);
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if (verbose)
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printf("cpu%d msr0x%x 0x%016llx -> 0x%016llx\n",
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cpu, MSR_IA32_ENERGY_PERF_BIAS, previous_msr, new_bias);
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return;
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}
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char *proc_stat = "/proc/stat";
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/*
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* run func() on every cpu in /dev/cpu
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*/
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void for_every_cpu(void (func)(int))
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{
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FILE *fp;
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int retval;
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fp = fopen(proc_stat, "r");
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if (fp == NULL) {
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perror(proc_stat);
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exit(1);
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}
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retval = fscanf(fp, "cpu %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n");
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if (retval != 0) {
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perror("/proc/stat format");
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exit(1);
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}
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while (1) {
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int cpu;
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retval = fscanf(fp,
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"cpu%u %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n",
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&cpu);
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if (retval != 1)
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return;
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func(cpu);
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}
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fclose(fp);
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}
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int main(int argc, char **argv)
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{
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cmdline(argc, argv);
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if (verbose > 1)
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printf("x86_energy_perf_policy Nov 24, 2010"
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" - Len Brown <lenb@kernel.org>\n");
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if (verbose > 1 && !read_only)
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printf("new_bias %lld\n", new_bias);
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validate_cpuid();
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if (cpu != -1) {
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if (read_only)
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print_msr(cpu);
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else
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update_msr(cpu);
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} else {
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if (read_only)
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for_every_cpu(print_msr);
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else
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for_every_cpu(update_msr);
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}
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return 0;
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}
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