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Linux/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c

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  1 /*
  2  *  (C) 2010,2011       Thomas Renninger <trenn@suse.de>, Novell Inc.
  3  *
  4  *  Licensed under the terms of the GNU GPL License version 2.
  5  */
  6 
  7 #if defined(__i386__) || defined(__x86_64__)
  8 
  9 #include <stdio.h>
 10 #include <stdint.h>
 11 #include <stdlib.h>
 12 #include <string.h>
 13 #include <limits.h>
 14 
 15 #include <cpufreq.h>
 16 
 17 #include "helpers/helpers.h"
 18 #include "idle_monitor/cpupower-monitor.h"
 19 
 20 #define MSR_APERF       0xE8
 21 #define MSR_MPERF       0xE7
 22 
 23 #define MSR_TSC 0x10
 24 
 25 #define MSR_AMD_HWCR 0xc0010015
 26 
 27 enum mperf_id { C0 = 0, Cx, AVG_FREQ, MPERF_CSTATE_COUNT };
 28 
 29 static int mperf_get_count_percent(unsigned int self_id, double *percent,
 30                                    unsigned int cpu);
 31 static int mperf_get_count_freq(unsigned int id, unsigned long long *count,
 32                                 unsigned int cpu);
 33 static struct timespec time_start, time_end;
 34 
 35 static cstate_t mperf_cstates[MPERF_CSTATE_COUNT] = {
 36         {
 37                 .name                   = "C0",
 38                 .desc                   = N_("Processor Core not idle"),
 39                 .id                     = C0,
 40                 .range                  = RANGE_THREAD,
 41                 .get_count_percent      = mperf_get_count_percent,
 42         },
 43         {
 44                 .name                   = "Cx",
 45                 .desc                   = N_("Processor Core in an idle state"),
 46                 .id                     = Cx,
 47                 .range                  = RANGE_THREAD,
 48                 .get_count_percent      = mperf_get_count_percent,
 49         },
 50 
 51         {
 52                 .name                   = "Freq",
 53                 .desc                   = N_("Average Frequency (including boost) in MHz"),
 54                 .id                     = AVG_FREQ,
 55                 .range                  = RANGE_THREAD,
 56                 .get_count              = mperf_get_count_freq,
 57         },
 58 };
 59 
 60 enum MAX_FREQ_MODE { MAX_FREQ_SYSFS, MAX_FREQ_TSC_REF };
 61 static int max_freq_mode;
 62 /*
 63  * The max frequency mperf is ticking at (in C0), either retrieved via:
 64  *   1) calculated after measurements if we know TSC ticks at mperf/P0 frequency
 65  *   2) cpufreq /sys/devices/.../cpu0/cpufreq/cpuinfo_max_freq at init time
 66  * 1. Is preferred as it also works without cpufreq subsystem (e.g. on Xen)
 67  */
 68 static unsigned long max_frequency;
 69 
 70 static unsigned long long tsc_at_measure_start;
 71 static unsigned long long tsc_at_measure_end;
 72 static unsigned long long *mperf_previous_count;
 73 static unsigned long long *aperf_previous_count;
 74 static unsigned long long *mperf_current_count;
 75 static unsigned long long *aperf_current_count;
 76 
 77 /* valid flag for all CPUs. If a MSR read failed it will be zero */
 78 static int *is_valid;
 79 
 80 static int mperf_get_tsc(unsigned long long *tsc)
 81 {
 82         int ret;
 83         ret = read_msr(0, MSR_TSC, tsc);
 84         if (ret)
 85                 dprint("Reading TSC MSR failed, returning %llu\n", *tsc);
 86         return ret;
 87 }
 88 
 89 static int mperf_init_stats(unsigned int cpu)
 90 {
 91         unsigned long long val;
 92         int ret;
 93 
 94         ret = read_msr(cpu, MSR_APERF, &val);
 95         aperf_previous_count[cpu] = val;
 96         ret |= read_msr(cpu, MSR_MPERF, &val);
 97         mperf_previous_count[cpu] = val;
 98         is_valid[cpu] = !ret;
 99 
100         return 0;
101 }
102 
103 static int mperf_measure_stats(unsigned int cpu)
104 {
105         unsigned long long val;
106         int ret;
107 
108         ret = read_msr(cpu, MSR_APERF, &val);
109         aperf_current_count[cpu] = val;
110         ret |= read_msr(cpu, MSR_MPERF, &val);
111         mperf_current_count[cpu] = val;
112         is_valid[cpu] = !ret;
113 
114         return 0;
115 }
116 
117 static int mperf_get_count_percent(unsigned int id, double *percent,
118                                    unsigned int cpu)
119 {
120         unsigned long long aperf_diff, mperf_diff, tsc_diff;
121         unsigned long long timediff;
122 
123         if (!is_valid[cpu])
124                 return -1;
125 
126         if (id != C0 && id != Cx)
127                 return -1;
128 
129         mperf_diff = mperf_current_count[cpu] - mperf_previous_count[cpu];
130         aperf_diff = aperf_current_count[cpu] - aperf_previous_count[cpu];
131 
132         if (max_freq_mode == MAX_FREQ_TSC_REF) {
133                 tsc_diff = tsc_at_measure_end - tsc_at_measure_start;
134                 *percent = 100.0 * mperf_diff / tsc_diff;
135                 dprint("%s: TSC Ref - mperf_diff: %llu, tsc_diff: %llu\n",
136                        mperf_cstates[id].name, mperf_diff, tsc_diff);
137         } else if (max_freq_mode == MAX_FREQ_SYSFS) {
138                 timediff = max_frequency * timespec_diff_us(time_start, time_end);
139                 *percent = 100.0 * mperf_diff / timediff;
140                 dprint("%s: MAXFREQ - mperf_diff: %llu, time_diff: %llu\n",
141                        mperf_cstates[id].name, mperf_diff, timediff);
142         } else
143                 return -1;
144 
145         if (id == Cx)
146                 *percent = 100.0 - *percent;
147 
148         dprint("%s: previous: %llu - current: %llu - (%u)\n",
149                 mperf_cstates[id].name, mperf_diff, aperf_diff, cpu);
150         dprint("%s: %f\n", mperf_cstates[id].name, *percent);
151         return 0;
152 }
153 
154 static int mperf_get_count_freq(unsigned int id, unsigned long long *count,
155                                 unsigned int cpu)
156 {
157         unsigned long long aperf_diff, mperf_diff, time_diff, tsc_diff;
158 
159         if (id != AVG_FREQ)
160                 return 1;
161 
162         if (!is_valid[cpu])
163                 return -1;
164 
165         mperf_diff = mperf_current_count[cpu] - mperf_previous_count[cpu];
166         aperf_diff = aperf_current_count[cpu] - aperf_previous_count[cpu];
167 
168         if (max_freq_mode == MAX_FREQ_TSC_REF) {
169                 /* Calculate max_freq from TSC count */
170                 tsc_diff = tsc_at_measure_end - tsc_at_measure_start;
171                 time_diff = timespec_diff_us(time_start, time_end);
172                 max_frequency = tsc_diff / time_diff;
173         }
174 
175         *count = max_frequency * ((double)aperf_diff / mperf_diff);
176         dprint("%s: Average freq based on %s maximum frequency:\n",
177                mperf_cstates[id].name,
178                (max_freq_mode == MAX_FREQ_TSC_REF) ? "TSC calculated" : "sysfs read");
179         dprint("max_frequency: %lu\n", max_frequency);
180         dprint("aperf_diff: %llu\n", aperf_diff);
181         dprint("mperf_diff: %llu\n", mperf_diff);
182         dprint("avg freq:   %llu\n", *count);
183         return 0;
184 }
185 
186 static int mperf_start(void)
187 {
188         int cpu;
189         unsigned long long dbg;
190 
191         clock_gettime(CLOCK_REALTIME, &time_start);
192         mperf_get_tsc(&tsc_at_measure_start);
193 
194         for (cpu = 0; cpu < cpu_count; cpu++)
195                 mperf_init_stats(cpu);
196 
197         mperf_get_tsc(&dbg);
198         dprint("TSC diff: %llu\n", dbg - tsc_at_measure_start);
199         return 0;
200 }
201 
202 static int mperf_stop(void)
203 {
204         unsigned long long dbg;
205         int cpu;
206 
207         for (cpu = 0; cpu < cpu_count; cpu++)
208                 mperf_measure_stats(cpu);
209 
210         mperf_get_tsc(&tsc_at_measure_end);
211         clock_gettime(CLOCK_REALTIME, &time_end);
212 
213         mperf_get_tsc(&dbg);
214         dprint("TSC diff: %llu\n", dbg - tsc_at_measure_end);
215 
216         return 0;
217 }
218 
219 /*
220  * Mperf register is defined to tick at P0 (maximum) frequency
221  *
222  * Instead of reading out P0 which can be tricky to read out from HW,
223  * we use TSC counter if it reliably ticks at P0/mperf frequency.
224  *
225  * Still try to fall back to:
226  * /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
227  * on older Intel HW without invariant TSC feature.
228  * Or on AMD machines where TSC does not tick at P0 (do not exist yet, but
229  * it's still double checked (MSR_AMD_HWCR)).
230  *
231  * On these machines the user would still get useful mperf
232  * stats when acpi-cpufreq driver is loaded.
233  */
234 static int init_maxfreq_mode(void)
235 {
236         int ret;
237         unsigned long long hwcr;
238         unsigned long min;
239 
240         if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_INV_TSC))
241                 goto use_sysfs;
242 
243         if (cpupower_cpu_info.vendor == X86_VENDOR_AMD) {
244                 /* MSR_AMD_HWCR tells us whether TSC runs at P0/mperf
245                  * freq.
246                  * A test whether hwcr is accessable/available would be:
247                  * (cpupower_cpu_info.family > 0x10 ||
248                  *   cpupower_cpu_info.family == 0x10 &&
249                  *   cpupower_cpu_info.model >= 0x2))
250                  * This should be the case for all aperf/mperf
251                  * capable AMD machines and is therefore safe to test here.
252                  * Compare with Linus kernel git commit: acf01734b1747b1ec4
253                  */
254                 ret = read_msr(0, MSR_AMD_HWCR, &hwcr);
255                 /*
256                  * If the MSR read failed, assume a Xen system that did
257                  * not explicitly provide access to it and assume TSC works
258                 */
259                 if (ret != 0) {
260                         dprint("TSC read 0x%x failed - assume TSC working\n",
261                                MSR_AMD_HWCR);
262                         return 0;
263                 } else if (1 & (hwcr >> 24)) {
264                         max_freq_mode = MAX_FREQ_TSC_REF;
265                         return 0;
266                 } else { /* Use sysfs max frequency if available */ }
267         } else if (cpupower_cpu_info.vendor == X86_VENDOR_INTEL) {
268                 /*
269                  * On Intel we assume mperf (in C0) is ticking at same
270                  * rate than TSC
271                  */
272                 max_freq_mode = MAX_FREQ_TSC_REF;
273                 return 0;
274         }
275 use_sysfs:
276         if (cpufreq_get_hardware_limits(0, &min, &max_frequency)) {
277                 dprint("Cannot retrieve max freq from cpufreq kernel "
278                        "subsystem\n");
279                 return -1;
280         }
281         max_freq_mode = MAX_FREQ_SYSFS;
282         max_frequency /= 1000; /* Default automatically to MHz value */
283         return 0;
284 }
285 
286 /*
287  * This monitor provides:
288  *
289  * 1) Average frequency a CPU resided in
290  *    This always works if the CPU has aperf/mperf capabilities
291  *
292  * 2) C0 and Cx (any sleep state) time a CPU resided in
293  *    Works if mperf timer stops ticking in sleep states which
294  *    seem to be the case on all current HW.
295  * Both is directly retrieved from HW registers and is independent
296  * from kernel statistics.
297  */
298 struct cpuidle_monitor mperf_monitor;
299 struct cpuidle_monitor *mperf_register(void)
300 {
301         if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_APERF))
302                 return NULL;
303 
304         if (init_maxfreq_mode())
305                 return NULL;
306 
307         /* Free this at program termination */
308         is_valid = calloc(cpu_count, sizeof(int));
309         mperf_previous_count = calloc(cpu_count, sizeof(unsigned long long));
310         aperf_previous_count = calloc(cpu_count, sizeof(unsigned long long));
311         mperf_current_count = calloc(cpu_count, sizeof(unsigned long long));
312         aperf_current_count = calloc(cpu_count, sizeof(unsigned long long));
313 
314         mperf_monitor.name_len = strlen(mperf_monitor.name);
315         return &mperf_monitor;
316 }
317 
318 void mperf_unregister(void)
319 {
320         free(mperf_previous_count);
321         free(aperf_previous_count);
322         free(mperf_current_count);
323         free(aperf_current_count);
324         free(is_valid);
325 }
326 
327 struct cpuidle_monitor mperf_monitor = {
328         .name                   = "Mperf",
329         .hw_states_num          = MPERF_CSTATE_COUNT,
330         .hw_states              = mperf_cstates,
331         .start                  = mperf_start,
332         .stop                   = mperf_stop,
333         .do_register            = mperf_register,
334         .unregister             = mperf_unregister,
335         .needs_root             = 1,
336         .overflow_s             = 922000000 /* 922337203 seconds TSC overflow
337                                                at 20GHz */
338 };
339 #endif /* #if defined(__i386__) || defined(__x86_64__) */
340 

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