From: Len Brown <len.brown@xxxxxxxxx> 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 this 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. Linux-2.6.36 added "epb" to /proc/cpuinfo to indicate if an x86 processor supports MSR_IA32_ENERGY_PERF_BIAS, though the kernel does not actually program the MSR. In March, 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". So in June, I proposed a generic user/kernel API to consolidate 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, 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 the same utility re-sent, this time proposed to reside in the kernel tools directory. Signed-off-by: Len Brown <len.brown@xxxxxxxxx> --- v2 create man page minor tweaks in response to review comments tools/power/x86/x86_energy_perf_policy/Makefile | 8 + .../x86_energy_perf_policy.8 | 104 +++++++ .../x86_energy_perf_policy.c | 325 ++++++++++++++++++++ diff --git a/tools/power/x86/x86_energy_perf_policy/Makefile b/tools/power/x86/x86_energy_perf_policy/Makefile new file mode 100644 index 0000000..f458237 --- /dev/null +++ b/tools/power/x86/x86_energy_perf_policy/Makefile @@ -0,0 +1,8 @@ +x86_energy_perf_policy : x86_energy_perf_policy.c + +clean : + rm -f x86_energy_perf_policy + +install : + install x86_energy_perf_policy /usr/bin/ + install x86_energy_perf_policy.8 /usr/share/man/man8/ 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 0000000..8eaaad6 --- /dev/null +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 @@ -0,0 +1,104 @@ +.\" This page Copyright (C) 2010 Len Brown <len.brown@xxxxxxxxx> +.\" Distributed under the GPL, Copyleft 1994. +.TH X86_ENERGY_PERF_POLICY 8 +.SH NAME +x86_energy_perf_policy \- read or write MSR_IA32_ENERGY_PERF_BIAS +.SH SYNOPSIS +.ft B +.B x86_energy_perf_policy +.RB [ "\-c cpu" ] +.RB [ "\-v" ] +.RB "\-r" +.br +.B x86_energy_perf_policy +.RB [ "\-c cpu" ] +.RB [ "\-v" ] +.RB 'performance' +.br +.B x86_energy_perf_policy +.RB [ "\-c cpu" ] +.RB [ "\-v" ] +.RB 'normal' +.br +.B x86_energy_perf_policy +.RB [ "\-c cpu" ] +.RB [ "\-v" ] +.RB 'powersave' +.br +.B x86_energy_perf_policy +.RB [ "\-c cpu" ] +.RB [ "\-v" ] +.RB n +.br +.SH DESCRIPTION +\fBx86_energy_perf_policy\fP +allows software to convey +its policy for the relative importance of performance +versus energy savings to the processor. + +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. + +.SS Options +\fB-c\fP 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. +.PP +\fB-v\fP increases verbosity. By default +x86_energy_perf_policy is silent. +.PP +\fB-r\fP is for "read-only" mode - the unchanged state +is read and displayed. +.PP +.I 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. +.PP +.I normal +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 reasonable default for most desktops and servers. +.PP +.I powersave +Set a policy where the processor can accept +a measurable performance hit to maximize energy efficiency. +.PP +.I 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 maximum energy efficiency. + +.SH NOTES +.B "x86_energy_perf_policy " +runs only as root. +.SH FILES +.ta +.nf +/dev/cpu/*/msr +.fi + +.SH "SEE ALSO" +msr(4) +.PP +.SH AUTHORS +.nf +Written by Len Brown <len.brown@xxxxxxxxx> diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c new file mode 100644 index 0000000..b539923 --- /dev/null +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c @@ -0,0 +1,325 @@ +/* + * x86_energy_perf_policy -- set the energy versus performance + * policy preference bias on recent X86 processors. + */ +/* + * Copyright (c) 2010, Intel Corporation. + * Len Brown <len.brown@xxxxxxxxx> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms and conditions of the GNU General Public License, + * version 2, as published by the Free Software Foundation. + * + * This program is distributed in the hope it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + * more details. + * + * You should have received a copy of the GNU General Public License along with + * this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include <stdio.h> +#include <unistd.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/resource.h> +#include <fcntl.h> +#include <signal.h> +#include <sys/time.h> +#include <stdlib.h> +#include <string.h> + +unsigned int verbose; /* set with -v */ +unsigned int read_only; /* set with -r */ +char *progname; +unsigned long long new_bias; +int cpu = -1; + +/* + * Usage: + * + * -c cpu: limit action to a single CPU (default is all CPUs) + * -v: verbose output (can invoke more than once) + * -r: read-only, don't change any settings + * + * performance + * Performance is paramount. + * Unwilling to sacrafice any performance + * for the sake of energy saving. (hardware default) + * + * normal + * Can tolerate minor performance compromise + * for potentially significant energy savings. + * (reasonable default for most desktops and servers) + * + * powersave + * Can tolerate significant performance hit + * to maximize energy savings. + * + * n + * a numerical value to write to the underlying MSR. + */ +void usage(void) +{ + printf("%s: [-c cpu] [-v] " + "(-r | 'performance' | 'normal' | 'powersave' | n)\n", + progname); + exit(1); +} + +#define MSR_IA32_ENERGY_PERF_BIAS 0x000001b0 + +#define BIAS_PERFORMANCE 0 +#define BIAS_BALANCE 6 +#define BIAS_POWERSAVE 15 + +void cmdline(int argc, char **argv) +{ + int opt; + + progname = argv[0]; + + while ((opt = getopt(argc, argv, "+rvc:")) != -1) { + switch (opt) { + case 'c': + cpu = atoi(optarg); + break; + case 'r': + read_only = 1; + break; + case 'v': + verbose++; + break; + default: + usage(); + } + } + /* if -r, then should be no additional optind */ + if (read_only && (argc > optind)) + usage(); + + /* + * if no -r , then must be one additional optind + */ + if (!read_only) { + + if (argc != optind + 1) { + printf("must supply -r or policy param\n"); + usage(); + } + + if (!strcmp("performance", argv[optind])) { + new_bias = BIAS_PERFORMANCE; + } else if (!strcmp("normal", argv[optind])) { + new_bias = BIAS_BALANCE; + } else if (!strcmp("powersave", argv[optind])) { + new_bias = BIAS_POWERSAVE; + } else { + char *endptr; + + new_bias = strtoull(argv[optind], &endptr, 0); + if (endptr == argv[optind] || + new_bias > BIAS_POWERSAVE) { + fprintf(stderr, "invalid value: %s\n", + argv[optind]); + usage(); + } + } + } +} + +/* + * validate_cpuid() + * returns on success, quietly exits on failure (make verbose with -v) + */ +void validate_cpuid(void) +{ + unsigned int eax, ebx, ecx, edx, max_level; + char brand[16]; + unsigned int fms, family, model, stepping; + + eax = ebx = ecx = edx = 0; + + asm("cpuid" : "=a" (max_level), "=b" (ebx), "=c" (ecx), + "=d" (edx) : "a" (0)); + + if (ebx != 0x756e6547 || edx != 0x49656e69 || ecx != 0x6c65746e) { + if (verbose) + fprintf(stderr, "%.4s%.4s%.4s != GenuineIntel", + (char *)&ebx, (char *)&edx, (char *)&ecx); + exit(1); + } + + asm("cpuid" : "=a" (fms), "=c" (ecx), "=d" (edx) : "a" (1) : "ebx"); + family = (fms >> 8) & 0xf; + model = (fms >> 4) & 0xf; + stepping = fms & 0xf; + if (family == 6 || family == 0xf) + model += ((fms >> 16) & 0xf) << 4; + + if (verbose > 1) + printf("CPUID %s %d levels family:model:stepping " + "0x%x:%x:%x (%d:%d:%d)\n", brand, max_level, + family, model, stepping, family, model, stepping); + + if (!(edx & (1 << 5))) { + if (verbose) + printf("CPUID: no MSR\n"); + exit(1); + } + + /* + * Support for MSR_IA32_ENERGY_PERF_BIAS + * is indicated by CPUID.06H.ECX.bit3 + */ + asm("cpuid" : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (6)); + if (verbose) + printf("CPUID.06H.ECX: 0x%x\n", ecx); + if (!(ecx & (1 << 3))) { + if (verbose) + printf("CPUID: No MSR_IA32_ENERGY_PERF_BIAS\n"); + exit(1); + } + return; /* success */ +} + +unsigned long long get_msr(int cpu, int offset) +{ + unsigned long long msr; + char msr_path[32]; + int retval; + int fd; + + sprintf(msr_path, "/dev/cpu/%d/msr", cpu); + fd = open(msr_path, O_RDONLY); + if (fd < 0) { + printf("Try \"# modprobe msr\"\n"); + perror(msr_path); + exit(1); + } + + retval = pread(fd, &msr, sizeof msr, offset); + + if (retval != sizeof msr) { + printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval); + exit(-2); + } + close(fd); + return msr; +} + +unsigned long long put_msr(int cpu, unsigned long long new_msr, int offset) +{ + unsigned long long old_msr; + char msr_path[32]; + int retval; + int fd; + + sprintf(msr_path, "/dev/cpu/%d/msr", cpu); + fd = open(msr_path, O_RDWR); + if (fd < 0) { + perror(msr_path); + exit(1); + } + + retval = pread(fd, &old_msr, sizeof old_msr, offset); + if (retval != sizeof old_msr) { + perror("pwrite"); + printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval); + exit(-2); + } + + retval = pwrite(fd, &new_msr, sizeof new_msr, offset); + if (retval != sizeof new_msr) { + perror("pwrite"); + printf("pwrite cpu%d 0x%x = %d\n", cpu, offset, retval); + exit(-2); + } + + close(fd); + + return old_msr; +} + +void print_msr(int cpu) +{ + printf("cpu%d: 0x%016llx\n", + cpu, get_msr(cpu, MSR_IA32_ENERGY_PERF_BIAS)); +} + +void update_msr(int cpu) +{ + unsigned long long previous_msr; + + previous_msr = put_msr(cpu, new_bias, MSR_IA32_ENERGY_PERF_BIAS); + + if (verbose) + printf("cpu%d msr0x%x 0x%016llx -> 0x%016llx\n", + cpu, MSR_IA32_ENERGY_PERF_BIAS, previous_msr, new_bias); + + return; +} + +char *proc_stat = "/proc/stat"; +/* + * run func() on every cpu in /dev/cpu + */ +void for_every_cpu(void (func)(int)) +{ + FILE *fp; + int retval; + + fp = fopen(proc_stat, "r"); + if (fp == NULL) { + perror(proc_stat); + exit(1); + } + + retval = fscanf(fp, "cpu %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n"); + if (retval != 0) { + perror("/proc/stat format"); + exit(1); + } + + while (1) { + int cpu; + + retval = fscanf(fp, + "cpu%u %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n", + &cpu); + if (retval != 1) + return; + + func(cpu); + } + fclose(fp); +} + +int main(int argc, char **argv) +{ + cmdline(argc, argv); + + if (verbose > 1) + printf("x86_energy_perf_policy Nov 24, 2010" + " - Len Brown <lenb@xxxxxxxxxx>\n"); + if (verbose > 1 && !read_only) + printf("new_bias %lld\n", new_bias); + + validate_cpuid(); + + if (cpu != -1) { + if (read_only) + print_msr(cpu); + else + update_msr(cpu); + } else { + if (read_only) + for_every_cpu(print_msr); + else + for_every_cpu(update_msr); + } + + return 0; +} _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
