2 * x86_energy_perf_policy -- set the energy versus performance
3 * policy preference bias on recent X86 processors.
6 * Copyright (c) 2010, Intel Corporation.
7 * Len Brown <len.brown@intel.com>
9 * This program is free software; you can redistribute it and/or modify it
10 * under the terms and conditions of the GNU General Public License,
11 * version 2, as published by the Free Software Foundation.
13 * This program is distributed in the hope it will be useful, but WITHOUT
14 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
18 * You should have received a copy of the GNU General Public License along with
19 * this program; if not, write to the Free Software Foundation, Inc.,
20 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
25 #include <sys/types.h>
27 #include <sys/resource.h>
34 unsigned int verbose; /* set with -v */
35 unsigned int read_only; /* set with -r */
37 unsigned long long new_bias;
43 * -c cpu: limit action to a single CPU (default is all CPUs)
44 * -v: verbose output (can invoke more than once)
45 * -r: read-only, don't change any settings
48 * Performance is paramount.
49 * Unwilling to sacrafice any performance
50 * for the sake of energy saving. (hardware default)
53 * Can tolerate minor performance compromise
54 * for potentially significant energy savings.
55 * (reasonable default for most desktops and servers)
58 * Can tolerate significant performance hit
59 * to maximize energy savings.
62 * a numerical value to write to the underlying MSR.
66 printf("%s: [-c cpu] [-v] "
67 "(-r | 'performance' | 'normal' | 'powersave' | n)\n",
72 #define MSR_IA32_ENERGY_PERF_BIAS 0x000001b0
74 #define BIAS_PERFORMANCE 0
75 #define BIAS_BALANCE 6
76 #define BIAS_POWERSAVE 15
78 void cmdline(int argc, char **argv)
84 while ((opt = getopt(argc, argv, "+rvc:")) != -1) {
99 /* if -r, then should be no additional optind */
100 if (read_only && (argc > optind))
104 * if no -r , then must be one additional optind
108 if (argc != optind + 1) {
109 printf("must supply -r or policy param\n");
113 if (!strcmp("performance", argv[optind])) {
114 new_bias = BIAS_PERFORMANCE;
115 } else if (!strcmp("normal", argv[optind])) {
116 new_bias = BIAS_BALANCE;
117 } else if (!strcmp("powersave", argv[optind])) {
118 new_bias = BIAS_POWERSAVE;
122 new_bias = strtoull(argv[optind], &endptr, 0);
123 if (endptr == argv[optind] ||
124 new_bias > BIAS_POWERSAVE) {
125 fprintf(stderr, "invalid value: %s\n",
135 * returns on success, quietly exits on failure (make verbose with -v)
137 void validate_cpuid(void)
139 unsigned int eax, ebx, ecx, edx, max_level;
141 unsigned int fms, family, model, stepping;
143 eax = ebx = ecx = edx = 0;
145 asm("cpuid" : "=a" (max_level), "=b" (ebx), "=c" (ecx),
146 "=d" (edx) : "a" (0));
148 if (ebx != 0x756e6547 || edx != 0x49656e69 || ecx != 0x6c65746e) {
150 fprintf(stderr, "%.4s%.4s%.4s != GenuineIntel",
151 (char *)&ebx, (char *)&edx, (char *)&ecx);
155 asm("cpuid" : "=a" (fms), "=c" (ecx), "=d" (edx) : "a" (1) : "ebx");
156 family = (fms >> 8) & 0xf;
157 model = (fms >> 4) & 0xf;
158 stepping = fms & 0xf;
159 if (family == 6 || family == 0xf)
160 model += ((fms >> 16) & 0xf) << 4;
163 printf("CPUID %s %d levels family:model:stepping "
164 "0x%x:%x:%x (%d:%d:%d)\n", brand, max_level,
165 family, model, stepping, family, model, stepping);
167 if (!(edx & (1 << 5))) {
169 printf("CPUID: no MSR\n");
174 * Support for MSR_IA32_ENERGY_PERF_BIAS
175 * is indicated by CPUID.06H.ECX.bit3
177 asm("cpuid" : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (6));
179 printf("CPUID.06H.ECX: 0x%x\n", ecx);
180 if (!(ecx & (1 << 3))) {
182 printf("CPUID: No MSR_IA32_ENERGY_PERF_BIAS\n");
185 return; /* success */
188 unsigned long long get_msr(int cpu, int offset)
190 unsigned long long msr;
195 sprintf(msr_path, "/dev/cpu/%d/msr", cpu);
196 fd = open(msr_path, O_RDONLY);
198 printf("Try \"# modprobe msr\"\n");
203 retval = pread(fd, &msr, sizeof msr, offset);
205 if (retval != sizeof msr) {
206 printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval);
213 unsigned long long put_msr(int cpu, unsigned long long new_msr, int offset)
215 unsigned long long old_msr;
220 sprintf(msr_path, "/dev/cpu/%d/msr", cpu);
221 fd = open(msr_path, O_RDWR);
227 retval = pread(fd, &old_msr, sizeof old_msr, offset);
228 if (retval != sizeof old_msr) {
230 printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval);
234 retval = pwrite(fd, &new_msr, sizeof new_msr, offset);
235 if (retval != sizeof new_msr) {
237 printf("pwrite cpu%d 0x%x = %d\n", cpu, offset, retval);
246 void print_msr(int cpu)
248 printf("cpu%d: 0x%016llx\n",
249 cpu, get_msr(cpu, MSR_IA32_ENERGY_PERF_BIAS));
252 void update_msr(int cpu)
254 unsigned long long previous_msr;
256 previous_msr = put_msr(cpu, new_bias, MSR_IA32_ENERGY_PERF_BIAS);
259 printf("cpu%d msr0x%x 0x%016llx -> 0x%016llx\n",
260 cpu, MSR_IA32_ENERGY_PERF_BIAS, previous_msr, new_bias);
265 char *proc_stat = "/proc/stat";
267 * run func() on every cpu in /dev/cpu
269 void for_every_cpu(void (func)(int))
274 fp = fopen(proc_stat, "r");
280 retval = fscanf(fp, "cpu %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n");
282 perror("/proc/stat format");
290 "cpu%u %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n",
300 int main(int argc, char **argv)
305 printf("x86_energy_perf_policy Nov 24, 2010"
306 " - Len Brown <lenb@kernel.org>\n");
307 if (verbose > 1 && !read_only)
308 printf("new_bias %lld\n", new_bias);
319 for_every_cpu(print_msr);
321 for_every_cpu(update_msr);