Roman Zippel wrote:
~
The thing that worries me about this function is that it does every
thing in usec. We are using nsec in xtime now and I wonder if it would
not be more accurate to do the math in nsecs. Even tick size
(tick_nsec) does not translate well to usec, it currently being 999849
nsecs.
George
---
kernel/time.c | 3 ++-
kernel/timer.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 55 insertions(+), 1 deletion(-)
Index: linux-2.6/kernel/time.c
===================================================================
--- linux-2.6.orig/kernel/time.c 2005-07-13 03:18:04.000000000 +0200
+++ linux-2.6/kernel/time.c 2005-08-16 01:37:20.000000000 +0200
@@ -366,8 +366,9 @@ int do_adjtimex(struct timex *txc)
} /* txc->modes & ADJ_OFFSET */
if (txc->modes & ADJ_TICK) {
tick_usec = txc->tick;
- tick_nsec = TICK_USEC_TO_NSEC(tick_usec);
}
+ if (txc->modes & (ADJ_FREQUENCY|ADJ_OFFSET|ADJ_TICK))
+ time_recalc();
} /* txc->modes */
leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0
|| ((time_status & (STA_PPSFREQ|STA_PPSTIME)) != 0
Index: linux-2.6/kernel/timer.c
===================================================================
--- linux-2.6.orig/kernel/timer.c 2005-07-13 03:18:04.000000000 +0200
+++ linux-2.6/kernel/timer.c 2005-08-16 23:10:53.000000000 +0200
@@ -559,6 +559,7 @@ found:
*/
unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */
unsigned long tick_nsec = TICK_NSEC; /* ACTHZ period (nsec) */
+unsigned long tick_nsec2 = TICK_NSEC;
/*
* The current time
@@ -569,6 +570,7 @@ unsigned long tick_nsec = TICK_NSEC; /*
* the usual normalization.
*/
struct timespec xtime __attribute__ ((aligned (16)));
+struct timespec xtime2 __attribute__ ((aligned (16)));
struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
EXPORT_SYMBOL(xtime);
@@ -596,6 +598,33 @@ static long time_adj; /* tick adjust (
long time_reftime; /* time at last adjustment (s) */
long time_adjust;
long time_next_adjust;
+static long time_adj2, time_adj2_cur, time_freq_adj2, time_freq_phase2,
time_phase2;
+
+void time_recalc(void)
+{
+ long f, t;
+ tick_nsec = TICK_USEC_TO_NSEC(tick_usec);
This leaves bits on the floor. Is it not possible to do this whole
calculation in nano seconds? Currently, for example, tick_nsec is 999849...
+
+ t = time_freq >> (SHIFT_USEC + 8);
+ if (t) {
+ time_freq -= t << (SHIFT_USEC + 8);
+ t *= 1000 << 8;
+ }
+ f = time_freq * 125;
+ t += tick_usec * USER_HZ * 1000 + (f >> (SHIFT_USEC - 3));
+ f &= (1 << (SHIFT_USEC - 3)) - 1;
+ tick_nsec2 = t / HZ;
+ f += (t % HZ) << (SHIFT_USEC - 3);
+ f <<= 5;
+ time_adj2 = f / HZ;
+ time_freq_adj2 = f % HZ;
+
+ printk("tr: %ld.%09ld(%ld,%ld,%ld,%ld) - %ld.%09ld(%ld,%ld,%ld)\n",
+ xtime.tv_sec, xtime.tv_sec,
+ tick_nsec, time_freq, time_offset, time_next_adjust,
+ xtime2.tv_sec, xtime2.tv_nsec,
+ tick_nsec2, time_adj2, time_freq_adj2);
+}
/*
* this routine handles the overflow of the microsecond field
@@ -739,6 +768,16 @@ static void second_overflow(void)
#endif
}
+static void second_overflow2(void)
+{
+ time_adj2_cur = time_adj2;
+ time_freq_phase2 += time_freq_adj2;
+ if (time_freq_phase2 > HZ) {
+ time_freq_phase2 -= HZ;
+ time_adj2_cur++;
+ }
+}
+
/* in the NTP reference this is called "hardclock()" */
static void update_wall_time_one_tick(void)
{
@@ -786,6 +825,20 @@ static void update_wall_time_one_tick(vo
time_adjust = time_next_adjust;
time_next_adjust = 0;
}
+
+ delta_nsec = tick_nsec2;
+ time_phase2 += time_adj2_cur;
+ if (time_phase2 >= (1 << (SHIFT_USEC + 2))) {
+ long ltemp = time_phase2 >> (SHIFT_USEC + 2);
+ time_phase2 -= ltemp << (SHIFT_USEC + 2);
+ delta_nsec += ltemp;
+ }
+ xtime2.tv_nsec += delta_nsec;
+ if (xtime2.tv_nsec >= NSEC_PER_SEC) {
+ xtime2.tv_nsec -= NSEC_PER_SEC;
+ xtime2.tv_sec++;
+ second_overflow2();
+ }
}
/*
-
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--
George Anzinger george@mvista.com
HRT (High-res-timers): http://sourceforge.net/projects/high-res-timers/
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