gettime.c

   1 /*
   2  * Clock functions
   3  */
   4
   5 #include <unistd.h>
   6 #include <math.h>
   7 #include <sys/time.h>
   8
   9 #include "fio.h"
  10 #include "smalloc.h"
  11
  12 #include "hash.h"
  13
  14 static unsigned long cycles_per_usec;
  15 static struct timeval last_tv;
  16 static unsigned long last_cycles;
  17 static int last_tv_valid;
  18
  19 static struct timeval *fio_tv;
  20 int fio_gtod_offload = 0;
  21 int fio_gtod_cpu = -1;
  22
  23 enum fio_cs fio_clock_source = CS_GTOD;
  24
  25 #ifdef FIO_DEBUG_TIME
  26
  27 #define HASH_BITS       8
  28 #define HASH_SIZE       (1 << HASH_BITS)
  29
  30 static struct flist_head hash[HASH_SIZE];
  31 static int gtod_inited;
  32
  33 struct gtod_log {
  34         struct flist_head list;
  35         void *caller;
  36         unsigned long calls;
  37 };
  38
  39 static struct gtod_log *find_hash(void *caller)
  40 {
  41         unsigned long h = hash_ptr(caller, HASH_BITS);
  42         struct flist_head *entry;
  43
  44         flist_for_each(entry, &hash[h]) {
  45                 struct gtod_log *log = flist_entry(entry, struct gtod_log,
  46                                                                         list);
  47
  48                 if (log->caller == caller)
  49                         return log;
  50         }
  51
  52         return NULL;
  53 }
  54
  55 static struct gtod_log *find_log(void *caller)
  56 {
  57         struct gtod_log *log = find_hash(caller);
  58
  59         if (!log) {
  60                 unsigned long h;
  61
  62                 log = malloc(sizeof(*log));
  63                 INIT_FLIST_HEAD(&log->list);
  64                 log->caller = caller;
  65                 log->calls = 0;
  66
  67                 h = hash_ptr(caller, HASH_BITS);
  68                 flist_add_tail(&log->list, &hash[h]);
  69         }
  70
  71         return log;
  72 }
  73
  74 static void gtod_log_caller(void *caller)
  75 {
  76         if (gtod_inited) {
  77                 struct gtod_log *log = find_log(caller);
  78
  79                 log->calls++;
  80         }
  81 }
  82
  83 static void fio_exit fio_dump_gtod(void)
  84 {
  85         unsigned long total_calls = 0;
  86         int i;
  87
  88         for (i = 0; i < HASH_SIZE; i++) {
  89                 struct flist_head *entry;
  90                 struct gtod_log *log;
  91
  92                 flist_for_each(entry, &hash[i]) {
  93                         log = flist_entry(entry, struct gtod_log, list);
  94
  95                         printf("function %p, calls %lu\n", log->caller,
  96                                                                 log->calls);
  97                         total_calls += log->calls;
  98                 }
  99         }
 100
 101         printf("Total %lu gettimeofday\n", total_calls);
 102 }
 103
 104 static void fio_init gtod_init(void)
 105 {
 106         int i;
 107
 108         for (i = 0; i < HASH_SIZE; i++)
 109                 INIT_FLIST_HEAD(&hash[i]);
 110
 111         gtod_inited = 1;
 112 }
 113
 114 #endif /* FIO_DEBUG_TIME */
 115
 116 #ifdef FIO_DEBUG_TIME
 117 void fio_gettime(struct timeval *tp, void *caller)
 118 #else
 119 void fio_gettime(struct timeval *tp, void fio_unused *caller)
 120 #endif
 121 {
 122 #ifdef FIO_DEBUG_TIME
 123         if (!caller)
 124                 caller = __builtin_return_address(0);
 125
 126         gtod_log_caller(caller);
 127 #endif
 128         if (fio_tv) {
 129                 memcpy(tp, fio_tv, sizeof(*tp));
 130                 return;
 131         }
 132
 133         switch (fio_clock_source) {
 134         case CS_GTOD:
 135                 gettimeofday(tp, NULL);
 136                 break;
 137         case CS_CGETTIME: {
 138                 struct timespec ts;
 139
 140                 if (clock_gettime(CLOCK_REALTIME, &ts) < 0) {
 141                         log_err("fio: clock_gettime fails\n");
 142                         assert(0);
 143                 }
 144
 145                 tp->tv_sec = ts.tv_sec;
 146                 tp->tv_usec = ts.tv_nsec / 1000;
 147                 break;
 148                 }
 149 #ifdef ARCH_HAVE_CPU_CLOCK
 150         case CS_CPUCLOCK: {
 151                 unsigned long long usecs, t;
 152
 153                 t = get_cpu_clock();
 154                 if (t < last_cycles) {
 155                         dprint(FD_TIME, "CPU clock going back in time\n");
 156                         t = last_cycles;
 157                 }
 158
 159                 usecs = t / cycles_per_usec;
 160                 tp->tv_sec = usecs / 1000000;
 161                 tp->tv_usec = usecs % 1000000;
 162                 last_cycles = t;
 163                 break;
 164                 }
 165 #endif
 166         default:
 167                 log_err("fio: invalid clock source %d\n", fio_clock_source);
 168                 break;
 169         }
 170
 171         /*
 172          * If Linux is using the tsc clock on non-synced processors,
 173          * sometimes time can appear to drift backwards. Fix that up.
 174          */
 175         if (last_tv_valid) {
 176                 if (tp->tv_sec < last_tv.tv_sec)
 177                         tp->tv_sec = last_tv.tv_sec;
 178                 else if (last_tv.tv_sec == tp->tv_sec &&
 179                          tp->tv_usec < last_tv.tv_usec)
 180                         tp->tv_usec = last_tv.tv_usec;
 181         }
 182         last_tv_valid = 1;
 183         memcpy(&last_tv, tp, sizeof(*tp));
 184 }
 185
 186 static unsigned long get_cycles_per_usec(void)
 187 {
 188         struct timeval s, e;
 189         unsigned long long c_s, c_e;
 190
 191         gettimeofday(&s, NULL);
 192         c_s = get_cpu_clock();
 193         do {
 194                 unsigned long long elapsed;
 195
 196                 gettimeofday(&e, NULL);
 197                 elapsed = utime_since(&s, &e);
 198                 if (elapsed >= 10) {
 199                         c_e = get_cpu_clock();
 200                         break;
 201                 }
 202         } while (1);
 203
 204         return c_e - c_s;
 205 }
 206
 207 void fio_clock_init(void)
 208 {
 209         double delta, mean, S;
 210         unsigned long avg, cycles[10];
 211         int i, samples;
 212
 213         last_tv_valid = 0;
 214
 215         cycles[0] = get_cycles_per_usec();
 216         S = delta = mean = 0.0;
 217         for (i = 0; i < 10; i++) {
 218                 cycles[i] = get_cycles_per_usec();
 219                 delta = cycles[i] - mean;
 220                 if (delta) {
 221                         mean += delta / (i + 1.0);
 222                         S += delta * (cycles[i] - mean);
 223                 }
 224         }
 225
 226         S = sqrt(S / (10 - 1.0));
 227
 228         samples = avg = 0;
 229         for (i = 0; i < 10; i++) {
 230                 double this = cycles[i];
 231
 232                 if ((max(this, mean) - min(this, mean)) > S)
 233                         continue;
 234                 samples++;
 235                 avg += this;
 236         }
 237
 238         S /= 10.0;
 239         mean /= 10.0;
 240
 241         for (i = 0; i < 10; i++)
 242                 dprint(FD_TIME, "cycles[%d]=%lu\n", i, cycles[i] / 10);
 243
 244         avg /= (samples * 10);
 245         dprint(FD_TIME, "avg: %lu\n", avg);
 246         dprint(FD_TIME, "mean=%f, S=%f\n", mean, S);
 247
 248         cycles_per_usec = avg;
 249 }
 250
 251 void fio_gtod_init(void)
 252 {
 253         fio_tv = smalloc(sizeof(struct timeval));
 254         assert(fio_tv);
 255 }
 256
 257 void fio_gtod_update(void)
 258 {
 259         gettimeofday(fio_tv, NULL);
 260 }