Re: timecounting: refactor fraction-to-nanosecond, bintime-to-nanosecond conversions

[Scott Cheloha]

On Tue, Jun 15, 2021 at 10:10:54AM -0500, Scott Cheloha wrote:
> 
> [...]
> 
> To tidy it up I'd like to refactor the fraction-to-nanosecond and
> bintime-to-nanosecond conversions into new functions so we only need
> to write them once.
> 
> ok?

Updated diff.  We can also use BINTIME_TO_NSEC() in tc_setclock().

Index: sys/time.h
===================================================================
RCS file: /cvs/src/sys/sys/time.h,v
retrieving revision 1.60
diff -u -p -r1.60 time.h
--- sys/time.h  15 Jun 2021 05:24:47 -0000      1.60
+++ sys/time.h  15 Jun 2021 20:39:52 -0000
@@ -222,11 +222,17 @@ bintimesub(const struct bintime *bt, con
  *   time_second ticks after N.999999999 not after N.4999999999
  */
 
+static inline uint32_t
+FRAC_TO_NSEC(uint64_t frac)
+{
+       return ((frac >> 32) * 1000000000ULL) >> 32;
+}
+
 static inline void
 BINTIME_TO_TIMESPEC(const struct bintime *bt, struct timespec *ts)
 {
        ts->tv_sec = bt->sec;
-       ts->tv_nsec = (long)(((uint64_t)1000000000 * (uint32_t)(bt->frac >> 
32)) >> 32);
+       ts->tv_nsec = FRAC_TO_NSEC(bt->frac);
 }
 
 static inline void
@@ -250,6 +256,12 @@ TIMEVAL_TO_BINTIME(const struct timeval 
        bt->sec = (time_t)tv->tv_sec;
        /* 18446744073709 = int(2^64 / 1000000) */
        bt->frac = (uint64_t)tv->tv_usec * (uint64_t)18446744073709ULL;
+}
+
+static inline uint64_t
+BINTIME_TO_NSEC(const struct bintime *bt)
+{
+       return bt->sec * 1000000000ULL + FRAC_TO_NSEC(bt->frac);
 }
 #endif
 
Index: kern/kern_tc.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_tc.c,v
retrieving revision 1.73
diff -u -p -r1.73 kern_tc.c
--- kern/kern_tc.c      15 Jun 2021 05:24:46 -0000      1.73
+++ kern/kern_tc.c      15 Jun 2021 20:39:53 -0000
@@ -254,28 +254,18 @@ uint64_t
 nsecuptime(void)
 {
        struct bintime bt;
-       uint64_t nsec;
 
        binuptime(&bt);
-
-       nsec = (1000000000ULL * (bt.frac >> 32)) >> 32;
-       nsec += bt.sec * 1000000000ULL;
-
-       return (nsec);
+       return BINTIME_TO_NSEC(&bt);
 }
 
 uint64_t
 getnsecuptime(void)
 {
        struct bintime bt;
-       uint64_t nsec;
 
        getbinuptime(&bt);
-
-       nsec = (1000000000ULL * (bt.frac >> 32)) >> 32;
-       nsec += bt.sec * 1000000000ULL;
-
-       return (nsec);
+       return BINTIME_TO_NSEC(&bt);
 }
 
 void
@@ -567,8 +557,7 @@ tc_setclock(const struct timespec *ts)
 #ifndef SMALL_KERNEL
        /* convert the bintime to ticks */
        bintimesub(&new_naptime, &old_naptime, &elapsed);
-       adj_ticks = (uint64_t)hz * elapsed.sec +
-           (((uint64_t)1000000 * (uint32_t)(elapsed.frac >> 32)) >> 32) / tick;
+       adj_ticks = BINTIME_TO_NSEC(&elapsed) / tick_nsec;
        if (adj_ticks > 0) {
                if (adj_ticks > INT_MAX)
                        adj_ticks = INT_MAX;