--- /dev/null
+.\" This page Copyright (C) 2010 Len Brown <len.brown@intel.com>
+.\" 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@intel.com>
--- /dev/null
+/*
+ * 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@intel.com>
+ *
+ * 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@kernel.org>\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;
+}
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