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x86_energy_perf_policy.c
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1 /*
2  * x86_energy_perf_policy -- set the energy versus performance
3  * policy preference bias on recent X86 processors.
4  */
5 /*
6  * Copyright (c) 2010, Intel Corporation.
7  * Len Brown <[email protected]>
8  *
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.
12  *
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
16  * more details.
17  *
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.
21  */
22 
23 #include <stdio.h>
24 #include <unistd.h>
25 #include <sys/types.h>
26 #include <sys/stat.h>
27 #include <sys/resource.h>
28 #include <fcntl.h>
29 #include <signal.h>
30 #include <sys/time.h>
31 #include <stdlib.h>
32 #include <string.h>
33 
34 unsigned int verbose; /* set with -v */
35 unsigned int read_only; /* set with -r */
36 char *progname;
37 unsigned long long new_bias;
38 int cpu = -1;
39 
40 /*
41  * Usage:
42  *
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
46  *
47  * performance
48  * Performance is paramount.
49  * Unwilling to sacrifice any performance
50  * for the sake of energy saving. (hardware default)
51  *
52  * normal
53  * Can tolerate minor performance compromise
54  * for potentially significant energy savings.
55  * (reasonable default for most desktops and servers)
56  *
57  * powersave
58  * Can tolerate significant performance hit
59  * to maximize energy savings.
60  *
61  * n
62  * a numerical value to write to the underlying MSR.
63  */
64 void usage(void)
65 {
66  printf("%s: [-c cpu] [-v] "
67  "(-r | 'performance' | 'normal' | 'powersave' | n)\n",
68  progname);
69  exit(1);
70 }
71 
72 #define MSR_IA32_ENERGY_PERF_BIAS 0x000001b0
73 
74 #define BIAS_PERFORMANCE 0
75 #define BIAS_BALANCE 6
76 #define BIAS_POWERSAVE 15
77 
78 void cmdline(int argc, char **argv)
79 {
80  int opt;
81 
82  progname = argv[0];
83 
84  while ((opt = getopt(argc, argv, "+rvc:")) != -1) {
85  switch (opt) {
86  case 'c':
87  cpu = atoi(optarg);
88  break;
89  case 'r':
90  read_only = 1;
91  break;
92  case 'v':
93  verbose++;
94  break;
95  default:
96  usage();
97  }
98  }
99  /* if -r, then should be no additional optind */
100  if (read_only && (argc > optind))
101  usage();
102 
103  /*
104  * if no -r , then must be one additional optind
105  */
106  if (!read_only) {
107 
108  if (argc != optind + 1) {
109  printf("must supply -r or policy param\n");
110  usage();
111  }
112 
113  if (!strcmp("performance", argv[optind])) {
115  } else if (!strcmp("normal", argv[optind])) {
117  } else if (!strcmp("powersave", argv[optind])) {
119  } else {
120  char *endptr;
121 
122  new_bias = strtoull(argv[optind], &endptr, 0);
123  if (endptr == argv[optind] ||
125  fprintf(stderr, "invalid value: %s\n",
126  argv[optind]);
127  usage();
128  }
129  }
130  }
131 }
132 
133 /*
134  * validate_cpuid()
135  * returns on success, quietly exits on failure (make verbose with -v)
136  */
137 void validate_cpuid(void)
138 {
139  unsigned int eax, ebx, ecx, edx, max_level;
140  unsigned int fms, family, model, stepping;
141 
142  eax = ebx = ecx = edx = 0;
143 
144  asm("cpuid" : "=a" (max_level), "=b" (ebx), "=c" (ecx),
145  "=d" (edx) : "a" (0));
146 
147  if (ebx != 0x756e6547 || edx != 0x49656e69 || ecx != 0x6c65746e) {
148  if (verbose)
149  fprintf(stderr, "%.4s%.4s%.4s != GenuineIntel",
150  (char *)&ebx, (char *)&edx, (char *)&ecx);
151  exit(1);
152  }
153 
154  asm("cpuid" : "=a" (fms), "=c" (ecx), "=d" (edx) : "a" (1) : "ebx");
155  family = (fms >> 8) & 0xf;
156  model = (fms >> 4) & 0xf;
157  stepping = fms & 0xf;
158  if (family == 6 || family == 0xf)
159  model += ((fms >> 16) & 0xf) << 4;
160 
161  if (verbose > 1)
162  printf("CPUID %d levels family:model:stepping "
163  "0x%x:%x:%x (%d:%d:%d)\n", max_level,
164  family, model, stepping, family, model, stepping);
165 
166  if (!(edx & (1 << 5))) {
167  if (verbose)
168  printf("CPUID: no MSR\n");
169  exit(1);
170  }
171 
172  /*
173  * Support for MSR_IA32_ENERGY_PERF_BIAS
174  * is indicated by CPUID.06H.ECX.bit3
175  */
176  asm("cpuid" : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (6));
177  if (verbose)
178  printf("CPUID.06H.ECX: 0x%x\n", ecx);
179  if (!(ecx & (1 << 3))) {
180  if (verbose)
181  printf("CPUID: No MSR_IA32_ENERGY_PERF_BIAS\n");
182  exit(1);
183  }
184  return; /* success */
185 }
186 
187 unsigned long long get_msr(int cpu, int offset)
188 {
189  unsigned long long msr;
190  char msr_path[32];
191  int retval;
192  int fd;
193 
194  sprintf(msr_path, "/dev/cpu/%d/msr", cpu);
195  fd = open(msr_path, O_RDONLY);
196  if (fd < 0) {
197  printf("Try \"# modprobe msr\"\n");
198  perror(msr_path);
199  exit(1);
200  }
201 
202  retval = pread(fd, &msr, sizeof msr, offset);
203 
204  if (retval != sizeof msr) {
205  printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval);
206  exit(-2);
207  }
208  close(fd);
209  return msr;
210 }
211 
212 unsigned long long put_msr(int cpu, unsigned long long new_msr, int offset)
213 {
214  unsigned long long old_msr;
215  char msr_path[32];
216  int retval;
217  int fd;
218 
219  sprintf(msr_path, "/dev/cpu/%d/msr", cpu);
220  fd = open(msr_path, O_RDWR);
221  if (fd < 0) {
222  perror(msr_path);
223  exit(1);
224  }
225 
226  retval = pread(fd, &old_msr, sizeof old_msr, offset);
227  if (retval != sizeof old_msr) {
228  perror("pwrite");
229  printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval);
230  exit(-2);
231  }
232 
233  retval = pwrite(fd, &new_msr, sizeof new_msr, offset);
234  if (retval != sizeof new_msr) {
235  perror("pwrite");
236  printf("pwrite cpu%d 0x%x = %d\n", cpu, offset, retval);
237  exit(-2);
238  }
239 
240  close(fd);
241 
242  return old_msr;
243 }
244 
245 void print_msr(int cpu)
246 {
247  printf("cpu%d: 0x%016llx\n",
249 }
250 
251 void update_msr(int cpu)
252 {
253  unsigned long long previous_msr;
254 
255  previous_msr = put_msr(cpu, new_bias, MSR_IA32_ENERGY_PERF_BIAS);
256 
257  if (verbose)
258  printf("cpu%d msr0x%x 0x%016llx -> 0x%016llx\n",
259  cpu, MSR_IA32_ENERGY_PERF_BIAS, previous_msr, new_bias);
260 
261  return;
262 }
263 
264 char *proc_stat = "/proc/stat";
265 /*
266  * run func() on every cpu in /dev/cpu
267  */
268 void for_every_cpu(void (func)(int))
269 {
270  FILE *fp;
271  int retval;
272 
273  fp = fopen(proc_stat, "r");
274  if (fp == NULL) {
275  perror(proc_stat);
276  exit(1);
277  }
278 
279  retval = fscanf(fp, "cpu %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n");
280  if (retval != 0) {
281  perror("/proc/stat format");
282  exit(1);
283  }
284 
285  while (1) {
286  int cpu;
287 
288  retval = fscanf(fp,
289  "cpu%u %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n",
290  &cpu);
291  if (retval != 1)
292  return;
293 
294  func(cpu);
295  }
296  fclose(fp);
297 }
298 
299 int main(int argc, char **argv)
300 {
301  cmdline(argc, argv);
302 
303  if (verbose > 1)
304  printf("x86_energy_perf_policy Nov 24, 2010"
305  " - Len Brown <[email protected]>\n");
306  if (verbose > 1 && !read_only)
307  printf("new_bias %lld\n", new_bias);
308 
309  validate_cpuid();
310 
311  if (cpu != -1) {
312  if (read_only)
313  print_msr(cpu);
314  else
315  update_msr(cpu);
316  } else {
317  if (read_only)
319  else
321  }
322 
323  return 0;
324 }