many changes to my_getsystime.c:

* my_getsystime() is only an interval timer. Its value can beused for calculating
  time intervals.
* renamed my_getsystime() to my_interval_timer(), to make the semantics
  clearer and let the compiler catch wrong usages of my_getsystime()
  (also future ones, that may come in merges).
* increased its granularity from 100ns to 1ns, old value was for UUID,
  but as UUID can no longer use it directly there is no need to downgrade
  the OS provided value
* fixed the UUID code to anchor the my_interval_timer() on the epoch, as
  required by the UUID standard. That is, this was only needed by UUID,
  and now I've moved it to UUID code from my_getsystime().
* fixed other wrong usages of my_getsystime() - e.g. in calculating
  times for pthread_cond_timedwait. It was buggy and could've caused
  long waits if OS clock would be changed.

client/mysqltest.cc

@@ -8516,7 +8516,7 @@ void timer_output(void)
 
 ulonglong timer_now(void)
 {
-  return my_micro_time() / 1000;
+  return my_interval_timer() / 1000000;
 }
 
 

include/my_pthread.h

@@ -426,9 +426,9 @@ int my_pthread_mutex_trylock(pthread_mutex_t *mutex);
 #ifndef set_timespec_nsec
 #define set_timespec_nsec(ABSTIME,NSEC) \
 { \
-  ulonglong now= my_getsystime() + (NSEC/100); \
-  (ABSTIME).ts_sec=  (now / ULL(10000000)); \
-  (ABSTIME).ts_nsec= (now % ULL(10000000) * 100 + ((NSEC) % 100)); \
+  ulonglong now= my_hrtime().val*1000 + (NSEC); \
+  (ABSTIME).ts_sec=  now / 1000000000ULL; \
+  (ABSTIME).ts_nsec= now % 1000000000ULL; \
 }
 #endif /* !set_timespec_nsec */
 #else
@@ -444,9 +444,9 @@ int my_pthread_mutex_trylock(pthread_mutex_t *mutex);
 #ifndef set_timespec_nsec
 #define set_timespec_nsec(ABSTIME,NSEC) \
 {\
-  ulonglong now= my_getsystime() + (NSEC/100); \
-  (ABSTIME).tv_sec=  (time_t) (now / ULL(10000000));                  \
-  (ABSTIME).tv_nsec= (long) (now % ULL(10000000) * 100 + ((NSEC) % 100)); \
+  ulonglong now= my_hrtime().val*1000 + (NSEC); \
+  (ABSTIME).tv_sec=  (time_t) (now / 1000000000ULL); \
+  (ABSTIME).tv_nsec= (long)   (now % 1000000000ULL); \
 }
 #endif /* !set_timespec_nsec */
 #endif /* HAVE_TIMESPEC_TS_SEC */

include/my_sys.h

@@ -894,21 +894,18 @@ extern ulong crc32(ulong crc, const uchar *buf, uint len);
 extern uint my_set_max_open_files(uint files);
 void my_free_open_file_info(void);
 
-#define HRTIME_RESOLUTION               1000000
+#define HRTIME_RESOLUTION               1000000  /* microseconds */
 typedef struct {ulonglong val;} my_hrtime_t;
-typedef struct {ulonglong val;} my_timediff_t;
 void my_time_init();
 extern my_hrtime_t my_hrtime();
-void my_diff_and_hrtime(my_timediff_t *interval, my_hrtime_t *timestamp);
-extern ulonglong my_getsystime(void);
+extern ulonglong my_interval_timer(void);
 
-#define my_micro_time()                 (my_getsystime()/10)
+#define microsecond_interval_timer()    (my_interval_timer()/1000)
 #define hrtime_to_time(X)               ((X).val/1000000)
 #define hrtime_from_time(X)             ((ulonglong)((X)*1000000ULL))
 #define hrtime_to_double(X)             ((X).val/(double)HRTIME_RESOLUTION)
 #define hrtime_sec_part(X)              ((ulong)((X).val%1000000))
 #define my_time(X)                      hrtime_to_time(my_hrtime())
-#define my_micro_and_hrtime(X,Y)        my_diff_and_hrtime(X,Y)
 
 extern my_bool my_gethwaddr(uchar *to);
 extern int my_getncpus();

mysys/my_getsystime.c

@@ -14,67 +14,66 @@
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
 
 
-/* 
-   TODO: in functions my_micro_time() and my_micro_time_and_time() there
-   exists some common code that should be merged into a function.
-*/
-
 #include "mysys_priv.h"
 #include "my_static.h"
 
 #ifdef __NETWARE__
 #include <nks/time.h>
 #elif defined(__WIN__)
-static ulonglong query_performance_frequency, query_performance_offset;
 #define OFFSET_TO_EPOC 116444736000000000LL
-#elif defined(HAVE_GETHRTIME)
-static ulonglong gethrtime_offset;
+static ulonglong query_performance_frequency;
 #endif
 
 /*
-  get time since epoc in 100 nanosec units
+  return number of nanoseconds since unspecified (but always the same)
+  point in the past
 
   NOTE:
   Thus to get the current time we should use the system function
   with the highest possible resolution
 
-  The value is not subject to resetting or drifting by way of adjtime() or
-  settimeofday(), and thus it is *NOT* appropriate for getting the current
-  timestamp. It can be used for calculating time intervals, though.
-  And it's good enough for UUID.
+  The value is not not anchored to any specific point in time (e.g. epoch) nor
+  is it subject to resetting or drifting by way of adjtime() or settimeofday(),
+  and thus it is *NOT* appropriate for getting the current timestamp. It can be
+  used for calculating time intervals, though.
 */
 
-ulonglong my_getsystime()
+ulonglong my_interval_timer()
 {
 #ifdef HAVE_CLOCK_GETTIME
   struct timespec tp;
-  clock_gettime(CLOCK_REALTIME, &tp);
-  return (ulonglong)tp.tv_sec*10000000+(ulonglong)tp.tv_nsec/100;
+  clock_gettime(CLOCK_MONOTONIC, &tp);
+  return tp.tv_sec*1000000000ULL+tp.tv_nsec;
 #elif defined(HAVE_GETHRTIME)
-  return gethrtime()/100-gethrtime_offset;
+  return gethrtime();
 #elif defined(__WIN__)
   LARGE_INTEGER t_cnt;
   if (query_performance_frequency)
   {
     QueryPerformanceCounter(&t_cnt);
-    return ((t_cnt.QuadPart / query_performance_frequency * 10000000) +
-            ((t_cnt.QuadPart % query_performance_frequency) * 10000000 /
-             query_performance_frequency) + query_performance_offset);
+    return (t_cnt.QuadPart / query_performance_frequency * 1000000000ULL) +
+            ((t_cnt.QuadPart % query_performance_frequency) * 1000000000ULL /
+             query_performance_frequency);
+  }
+  else
+  {
+    ulonglong newtime;
+    GetSystemTimeAsFileTime((FILETIME*)&newtime);
+    return newtime*100ULL;
   }
-  return 0;
 #elif defined(__NETWARE__)
   NXTime_t tm;
   NXGetTime(NX_SINCE_1970, NX_NSECONDS, &tm);
-  return (ulonglong)tm/100;
+  return (ulonglong)tm;
 #else
   /* TODO: check for other possibilities for hi-res timestamping */
   struct timeval tv;
   gettimeofday(&tv,NULL);
-  return (ulonglong)tv.tv_sec*10000000+(ulonglong)tv.tv_usec*10;
+  return tv.tv_sec*1000000000ULL+tv.tv_usec*1000ULL;
 #endif
 }
 
-/* Return current time in microseconds since epoch */
+/* Return current time in HRTIME_RESOLUTION (microseconds) since epoch */
 
 my_hrtime_t my_hrtime()
 {
@@ -84,60 +83,24 @@ my_hrtime_t my_hrtime()
   GetSystemTimeAsFileTime((FILETIME*)&newtime);
   newtime -= OFFSET_TO_EPOC;
   hrtime.val= newtime/10;
-#elif defined(HAVE_GETHRTIME)
-  struct timeval t;
-  /*
-    The following loop is here because gettimeofday may fail on some systems
-  */
-  while (gettimeofday(&t, NULL) != 0)
-  {}
-  hrtime.val= t.tv_sec*1000000 + t.tv_usec;
+#elif defined(HAVE_CLOCK_GETTIME)
+  struct timespec tp;
+  clock_gettime(CLOCK_REALTIME, &tp);
+  return tp.tv_sec*1000000ULL+tp.tv_nsec/1000ULL;
 #else
-  hrtime.val= my_getsystime()/10;
+  struct timeval t;
+  /* The following loop is here because gettimeofday may fail on some systems */
+  while (gettimeofday(&t, NULL) != 0) {}
+  hrtime.val= t.tv_sec*1000000ULL + t.tv_usec;
 #endif
   return hrtime;
 }
 
-/*
-  This function is basically equivalent to
-
-     *interval= my_getsystime()/10;
-     *timestamp= my_time();
-
-   but it avoids calling OS time functions twice, if possible.
-*/
-void my_diff_and_hrtime(my_timediff_t *interval, my_hrtime_t *timestamp)
-{
-  interval->val= my_getsystime() / 10;
-#if defined(__WIN__) || defined(HAVE_GETHRTIME)
-  *timestamp= my_hrtime();
-#else
-  timestamp->val= interval->val;
-#endif
-}
-
 void my_time_init()
 {
 #ifdef __WIN__
-  FILETIME ft;
-  LARGE_INTEGER li, t_cnt;
-  DBUG_ASSERT(sizeof(LARGE_INTEGER) == sizeof(query_performance_frequency));
+  compile_time_assert(sizeof(LARGE_INTEGER) == sizeof(query_performance_frequency));
   if (QueryPerformanceFrequency((LARGE_INTEGER *)&query_performance_frequency) == 0)
     query_performance_frequency= 0;
-  else
-  {
-    GetSystemTimeAsFileTime(&ft);
-    li.LowPart=  ft.dwLowDateTime;
-    li.HighPart= ft.dwHighDateTime;
-    query_performance_offset= li.QuadPart-OFFSET_TO_EPOC;
-    QueryPerformanceCounter(&t_cnt);
-    query_performance_offset-= (t_cnt.QuadPart /
-                                query_performance_frequency * 10000000 +
-                                t_cnt.QuadPart %
-                                query_performance_frequency * 10000000 /
-                                query_performance_frequency);
-  }
-#elif defined(HAVE_GETHRTIME)
-  gethrtime_offset= gethrtime();
 #endif
 }

mysys/queues.c

@@ -596,15 +596,15 @@ bool do_test(uint no_parts, uint l_max_ind, bool l_fix_used)
 
 static void start_measurement()
 {
-  start_time= my_getsystime();
+  start_time= my_interval_timer();
 }
 
 static void stop_measurement()
 {
-  ulonglong stop_time= my_getsystime();
+  ulonglong stop_time= my_interval_timer();
   uint time_in_micros;
   stop_time-= start_time;
-  stop_time/= 10; /* Convert to microseconds */
+  stop_time/= 1000; /* Convert to microseconds */
   time_in_micros= (uint)stop_time;
   printf("Time expired is %u microseconds \n", time_in_micros);
 }

sql/item_strfunc.cc

@@ -3446,6 +3446,8 @@ err:
 static struct rand_struct uuid_rand;
 static uint nanoseq;
 static ulonglong uuid_time=0;
+static longlong interval_timer_offset;
+
 static char clock_seq_and_node_str[]="-0000-000000000000";
 
 /**
@@ -3473,6 +3475,7 @@ static void set_clock_seq_str()
   uint16 clock_seq= ((uint)(my_rnd(&uuid_rand)*16383)) | UUID_VARIANT;
   tohex(clock_seq_and_node_str+1, clock_seq, 4);
   nanoseq= 0;
+  interval_timer_offset= my_hrtime().val * 10 - my_interval_timer()/100 + UUID_TIME_OFFSET;
 }
 
 String *Item_func_uuid::val_str(String *str)
@@ -3512,7 +3515,7 @@ String *Item_func_uuid::val_str(String *str)
     set_clock_seq_str();
   }
 
-  ulonglong tv= my_getsystime() + UUID_TIME_OFFSET + nanoseq;
+  ulonglong tv= my_interval_timer()/100 + interval_timer_offset + nanoseq;
 
   if (likely(tv > uuid_time))
   {
@@ -3564,7 +3567,7 @@ String *Item_func_uuid::val_str(String *str)
         irrelevant in the new numberspace.
       */
       set_clock_seq_str();
-      tv= my_getsystime() + UUID_TIME_OFFSET;
+      tv= my_interval_timer()/100 + interval_timer_offset;
       nanoseq= 0;
       DBUG_PRINT("uuid",("making new numberspace"));
     }

sql/mysqld.cc

@@ -1947,7 +1947,7 @@ static bool cache_thread()
         this thread for handling of new THD object/connection.
       */
       thd->mysys_var->abort= 0;
-      thd->thr_create_utime= my_micro_time();
+      thd->thr_create_utime= microsecond_interval_timer();
       threads.append(thd);
       return(1);
     }
@@ -4907,7 +4907,7 @@ void handle_connection_in_main_thread(THD *thd)
   thread_cache_size=0;			// Safety
   threads.append(thd);
   pthread_mutex_unlock(&LOCK_thread_count);
-  thd->start_utime= my_micro_time();
+  thd->start_utime= microsecond_interval_timer();
   handle_one_connection(thd);
 }
 
@@ -4933,7 +4933,7 @@ void create_thread_to_handle_connection(THD *thd)
     thread_created++;
     threads.append(thd);
     DBUG_PRINT("info",(("creating thread %lu"), thd->thread_id));
-    thd->prior_thr_create_utime= thd->start_utime= my_micro_time();
+    thd->prior_thr_create_utime= thd->start_utime= microsecond_interval_timer();
     if ((error=pthread_create(&thd->real_id,&connection_attrib,
                               handle_one_connection,
                               (void*) thd)))

sql/sql_class.h

@@ -2028,17 +2028,14 @@ public:
     {
       start_time= hrtime_to_my_time(user_time);
       start_time_sec_part= hrtime_sec_part(user_time);
-      start_utime= utime_after_lock= my_micro_time();
     }
     else
     {
-      my_hrtime_t hrtime;
-      my_timediff_t timediff;
-      my_micro_and_hrtime(&timediff, &hrtime);
+      my_hrtime_t hrtime= my_hrtime();
       start_time= hrtime_to_my_time(hrtime);
       start_time_sec_part= hrtime_sec_part(hrtime);
-      utime_after_lock= start_utime= timediff.val;
     }
+    start_utime= utime_after_lock= microsecond_interval_timer();
   }
   inline void	set_current_time()
   {
@@ -2051,15 +2048,15 @@ public:
     user_time= t;
     start_time= hrtime_to_my_time(user_time);
     start_time_sec_part= hrtime_sec_part(user_time);
-    start_utime= utime_after_lock= my_micro_time();
+    start_utime= utime_after_lock= microsecond_interval_timer();
   }
   inline void	set_time(my_time_t t, ulong sec_part)
   {
     my_hrtime_t hrtime= { hrtime_from_time(t) + sec_part };
     set_time(hrtime);
   }
-  void set_time_after_lock()  { utime_after_lock= my_micro_time(); }
-  ulonglong current_utime()  { return my_micro_time(); }
+  void set_time_after_lock()  { utime_after_lock= microsecond_interval_timer(); }
+  ulonglong current_utime()  { return microsecond_interval_timer(); }
   inline ulonglong found_rows(void)
   {
     return limit_found_rows;

sql/sql_connect.cc

@@ -1084,7 +1084,7 @@ pthread_handler_t handle_one_connection(void *arg)
 {
   THD *thd= (THD*) arg;
 
-  thd->thr_create_utime= my_micro_time();
+  thd->thr_create_utime= microsecond_interval_timer();
 
   if (thread_scheduler.init_new_connection_thread())
   {

sql/sql_profile.cc

@@ -221,7 +221,7 @@ void PROF_MEASUREMENT::set_label(const char *status_arg,
 */
 void PROF_MEASUREMENT::collect()
 {
-  time_usecs= (double) my_getsystime() / 10.0;  /* 1 sec was 1e7, now is 1e6 */
+  time_usecs= my_interval_timer() / 1e3;  /* ns to us */
 #ifdef HAVE_GETRUSAGE
   getrusage(RUSAGE_SELF, &rusage);
 #endif