MDEV-23175: my_timer_milliseconds ftime deprecated - clock_gettime replacement

Linux glibc has deprecated ftime resutlting in a compile error on Fedora-32.

Per manual clock_gettime is the suggested replacement. Because my_timer_milliseconds
is a relative time used by largely the perfomrance schema, CLOCK_MONOTONIC_COARSE
is used. This has been available since Linux-2.6.32.

The low overhead is shows in the unittest:

    $ unittest/mysys/my_rdtsc-t
    1..11
    # ----- Routine ---------------
    # myt.cycles.routine          :             5
    # myt.nanoseconds.routine     :            11
    # myt.microseconds.routine    :            13
    # myt.milliseconds.routine    :            18
    # myt.ticks.routine           :            17
    # ----- Frequency -------------
    # myt.cycles.frequency        :    3596597014
    # myt.nanoseconds.frequency   :    1000000000
    # myt.microseconds.frequency  :       1000000
    # myt.milliseconds.frequency  :          1039
    # myt.ticks.frequency         :           103
    # ----- Resolution ------------
    # myt.cycles.resolution       :             1
    # myt.nanoseconds.resolution  :             1
    # myt.microseconds.resolution :             1
    # myt.milliseconds.resolution :             1
    # myt.ticks.resolution        :             1
    # ----- Overhead --------------
    # myt.cycles.overhead         :           118
    # myt.nanoseconds.overhead    :           234
    # myt.microseconds.overhead   :           222
    # myt.milliseconds.overhead   :            30
    # myt.ticks.overhead          :          4946
    ok 1 - my_timer_init() did not crash
    ok 2 - The cycle timer is strictly increasing
    ok 3 - The cycle timer is implemented
    ok 4 - The nanosecond timer is increasing
    ok 5 - The nanosecond timer is implemented
    ok 6 - The microsecond timer is increasing
    ok 7 - The microsecond timer is implemented
    ok 8 - The millisecond timer is increasing
    ok 9 - The millisecond timer is implemented
    ok 10 - The tick timer is increasing
    ok 11 - The tick timer is implemented

configure.cmake

@@ -441,9 +441,12 @@ CHECK_INCLUDE_FILES(ia64intrin.h HAVE_IA64INTRIN_H)
 CHECK_FUNCTION_EXISTS(times HAVE_TIMES)
 CHECK_FUNCTION_EXISTS(gettimeofday HAVE_GETTIMEOFDAY)
 CHECK_FUNCTION_EXISTS(read_real_time HAVE_READ_REAL_TIME)
-# This should work on AIX.
 
+IF(NOT HAVE_CLOCK_GETTIME)
+# This should work on AIX.
 CHECK_FUNCTION_EXISTS(ftime HAVE_FTIME)
+ENDIF()
+
 # This is still a normal call for milliseconds.
 
 CHECK_FUNCTION_EXISTS(time HAVE_TIME)

mysys/my_rdtsc.c

@@ -75,7 +75,7 @@
 #endif
 #endif
 
-#if defined(HAVE_SYS_TIMEB_H) && defined(HAVE_FTIME)
+#if !defined(CLOCK_GETTIME) && defined(HAVE_SYS_TIMEB_H) && defined(HAVE_FTIME)
 #include <sys/timeb.h>       /* for ftime */
 #endif
 
@@ -175,7 +175,17 @@ ulonglong my_timer_microseconds(void)
 
 ulonglong my_timer_milliseconds(void)
 {
-#if defined(HAVE_SYS_TIMEB_H) && defined(HAVE_FTIME)
+#if defined(HAVE_CLOCK_GETTIME)
+  struct timespec tp;
+#ifdef CLOCK_MONOTONIC_COARSE
+  /* Linux */
+  clock_gettime(CLOCK_MONOTONIC_COARSE, &tp);
+#else
+  /* POSIX */
+  clock_gettime(CLOCK_MONOTONIC, &tp);
+#endif
+  return (ulonglong)tp.tv_sec * 1000 + (ulonglong)tp.tv_nsec / 1000000;
+#elif defined(HAVE_SYS_TIMEB_H) && defined(HAVE_FTIME)
   /* ftime() is obsolete but maybe the platform is old */
   struct timeb ft;
   ftime(&ft);