include/ust/clock.h

   1 /* Copyright (C) 2010  Pierre-Marc Fournier
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public
   5  * License as published by the Free Software Foundation; either
   6  * version 2.1 of the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
  16  */
  17
  18 #ifndef _UST_CLOCK_H
  19 #define _UST_CLOCK_H
  20
  21 #include <time.h>
  22 #include <sys/time.h>
  23 #include <stdint.h>
  24 #include <stddef.h>
  25 #include <ust/core.h>
  26
  27 /* TRACE CLOCK */
  28
  29 /* There are two types of clocks that can be used.
  30    - TSC based clock
  31    - gettimeofday() clock
  32
  33    Microbenchmarks on Linux 2.6.30 on Core2 Duo 3GHz (functions are inlined):
  34          Calls (100000000) to tsc(): 4004035641 cycles or 40 cycles/call
  35          Calls (100000000) to gettimeofday(): 9723158352 cycles or 97 cycles/call
  36
  37    For merging traces with the kernel, a time source compatible with that of
  38    the kernel is necessary.
  39
  40    Instead of gettimeofday(), we are now using clock_gettime for better
  41    precision and monotonicity.
  42 */
  43
  44 /* Only available for x86 arch */
  45 #define CLOCK_TRACE_FREQ  14
  46 #define CLOCK_TRACE  15
  47 union lttng_timespec {
  48         struct timespec ts;
  49         uint64_t lttng_ts;
  50 };
  51
  52 extern int ust_clock_source;
  53
  54 /* Choosing correct trace clock */
  55
  56 static __inline__ uint64_t trace_clock_read64(void)
  57 {
  58         struct timespec ts;
  59         uint64_t retval;
  60         union lttng_timespec *lts = (union lttng_timespec *) &ts;
  61
  62         clock_gettime(ust_clock_source, &ts);
  63         /*
  64          * Clock source can change when loading the binary (tracectl.c)
  65          * so we must check if the clock source has changed before
  66          * returning the correct value
  67          */
  68         if (likely(ust_clock_source == CLOCK_TRACE)) {
  69                 retval = lts->lttng_ts;
  70         } else { /* CLOCK_MONOTONIC */
  71                 retval = ts.tv_sec;
  72                 retval *= 1000000000;
  73                 retval += ts.tv_nsec;
  74         }
  75
  76         return retval;
  77 }
  78
  79 #if __i386__ || __x86_64__
  80 static __inline__ uint64_t trace_clock_frequency(void)
  81 {
  82         struct timespec ts;
  83         union lttng_timespec *lts = (union lttng_timespec *) &ts;
  84
  85         if (likely(ust_clock_source == CLOCK_TRACE)) {
  86                 clock_gettime(CLOCK_TRACE_FREQ, &ts);
  87                 return lts->lttng_ts;
  88         }
  89         return 1000000000LL;
  90 }
  91 #else /* #if __i386__ || __x86_64__ */
  92 static __inline__ uint64_t trace_clock_frequency(void)
  93 {
  94         return 1000000000LL;
  95 }
  96 #endif /* #else #if __i386__ || __x86_64__ */
  97
  98 static __inline__ uint32_t trace_clock_freq_scale(void)
  99 {
 100         return 1;
 101 }
 102
 103 #endif /* _UST_CLOCK_H */