[NTP 0/9] NTP patches

[NTP 0/9] NTP patches

[zippel]

Hi,

Here is my current version of the NTP patches.
They precalculate as much possible and get rid of a lot of rather crude
compensation code. The tick length is now a much simpler value, updated
once a second, which greatly reduces the dependency on HZ.
I rebased the patches against current -mm + John's ntp.c patch.

bye, Roman

--

[NTP 1/9] add ntp_update_frequency

[zippel]

[-- Attachment #1: 0001-NTP-add-ntp_update_frequency.txt --]
[-- Type: text/plain, Size: 4986 bytes --]

This introduces ntp_update_frequency() and deinlines ntp_clear() (as
it's not performance critical).
ntp_update_frequency() calculates the base tick length using tick_usec
and adds a base adjustment, in case the frequency doesn't divide evenly
by HZ.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
---
 include/linux/timex.h |   14 ++------------
 kernel/time/ntp.c     |   50 ++++++++++++++++++++++++++++++++++++++++++++------
 kernel/timer.c        |   11 ++++-------
 3 files changed, 50 insertions(+), 25 deletions(-)

Index: linux-2.6-mm/include/linux/timex.h
===================================================================
--- linux-2.6-mm.orig/include/linux/timex.h
+++ linux-2.6-mm/include/linux/timex.h
@@ -218,18 +218,8 @@ extern long time_reftime;	/* time at las
 extern long time_adjust;	/* The amount of adjtime left */
 extern long time_next_adjust;	/* Value for time_adjust at next tick */
 
-/**
- * ntp_clear - Clears the NTP state variables
- *
- * Must be called while holding a write on the xtime_lock
- */
-static inline void ntp_clear(void)
-{
-	time_adjust = 0;		/* stop active adjtime() */
-	time_status |= STA_UNSYNC;
-	time_maxerror = NTP_PHASE_LIMIT;
-	time_esterror = NTP_PHASE_LIMIT;
-}
+extern void ntp_clear(void);
+extern void ntp_update_frequency(void);
 
 /**
  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
Index: linux-2.6-mm/kernel/time/ntp.c
===================================================================
--- linux-2.6-mm.orig/kernel/time/ntp.c
+++ linux-2.6-mm/kernel/time/ntp.c
@@ -21,6 +21,13 @@ void time_interpolator_update(long delta
 #define time_interpolator_update(x)
 #endif
 
+/*
+ * Timekeeping variables
+ */
+unsigned long tick_usec = TICK_USEC; 		/* USER_HZ period (usec) */
+unsigned long tick_nsec;			/* ACTHZ period (nsec) */
+static u64 tick_length, tick_length_base;
+
 /* Don't completely fail for HZ > 500.  */
 int tickadj = 500/HZ ? : 1;		/* microsecs */
 
@@ -43,6 +50,36 @@ long time_reftime;			/* time at last adj
 long time_adjust;
 long time_next_adjust;
 
+/**
+ * ntp_clear - Clears the NTP state variables
+ *
+ * Must be called while holding a write on the xtime_lock
+ */
+void ntp_clear(void)
+{
+	time_adjust = 0;		/* stop active adjtime() */
+	time_status |= STA_UNSYNC;
+	time_maxerror = NTP_PHASE_LIMIT;
+	time_esterror = NTP_PHASE_LIMIT;
+
+	ntp_update_frequency();
+
+	tick_length = tick_length_base;
+}
+
+#define CLOCK_TICK_OVERFLOW	(LATCH * HZ - CLOCK_TICK_RATE)
+#define CLOCK_TICK_ADJUST	(((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / CLOCK_TICK_RATE)
+
+void ntp_update_frequency(void)
+{
+	tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT;
+	tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
+
+	do_div(tick_length_base, HZ);
+
+	tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT;
+}
+
 /*
  * this routine handles the overflow of the microsecond field
  *
@@ -157,6 +194,7 @@ void second_overflow(void)
 	 */
 	time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
 #endif
+	tick_length = tick_length_base;
 }
 
 /*
@@ -210,14 +248,13 @@ void update_ntp_one_tick(void)
  */
 u64 current_tick_length(void)
 {
-	long delta_nsec;
 	u64 ret;
 
 	/* calculate the finest interval NTP will allow.
 	 *    ie: nanosecond value shifted by (SHIFT_SCALE - 10)
 	 */
-	delta_nsec = tick_nsec + adjtime_adjustment() * 1000;
-	ret = (u64)delta_nsec << TICK_LENGTH_SHIFT;
+	ret = tick_length;
+	ret += (u64)(adjtime_adjustment() * 1000) << TICK_LENGTH_SHIFT;
 	ret += (s64)time_adj << (TICK_LENGTH_SHIFT - (SHIFT_SCALE - 10));
 
 	return ret;
@@ -357,10 +394,11 @@ int do_adjtimex(struct timex *txc)
 		    time_freq = max(time_freq, -time_tolerance);
 		} /* STA_PLL */
 	    } /* txc->modes & ADJ_OFFSET */
-	    if (txc->modes & ADJ_TICK) {
+	    if (txc->modes & ADJ_TICK)
 		tick_usec = txc->tick;
-		tick_nsec = TICK_USEC_TO_NSEC(tick_usec);
-	    }
+
+	    if (txc->modes & ADJ_TICK)
+		    ntp_update_frequency();
 	} /* txc->modes */
 leave:	if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
 		result = TIME_ERROR;
Index: linux-2.6-mm/kernel/timer.c
===================================================================
--- linux-2.6-mm.orig/kernel/timer.c
+++ linux-2.6-mm/kernel/timer.c
@@ -568,12 +568,6 @@ found:
 
 /******************************************************************/
 
-/*
- * Timekeeping variables
- */
-unsigned long tick_usec = TICK_USEC; 		/* USER_HZ period (usec) */
-unsigned long tick_nsec = TICK_NSEC;		/* ACTHZ period (nsec) */
-
 /* 
  * The current time 
  * wall_to_monotonic is what we need to add to xtime (or xtime corrected 
@@ -763,10 +757,13 @@ void __init timekeeping_init(void)
 	unsigned long flags;
 
 	write_seqlock_irqsave(&xtime_lock, flags);
+
+	ntp_clear();
+
 	clock = clocksource_get_next();
 	clocksource_calculate_interval(clock, tick_nsec);
 	clock->cycle_last = clocksource_read(clock);
-	ntp_clear();
+
 	write_sequnlock_irqrestore(&xtime_lock, flags);
 }
 

--

[NTP 2/9] add time_adj to tick length

[zippel]

[-- Attachment #1: 0002-NTP-add-time_adj-to-tick-length.txt --]
[-- Type: text/plain, Size: 1658 bytes --]

This makes time_adj local to second_overflow() and integrates it into
the tick length instead of adding it everytime.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
---
 kernel/time/ntp.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

Index: linux-2.6-mm/kernel/time/ntp.c
===================================================================
--- linux-2.6-mm.orig/kernel/time/ntp.c
+++ linux-2.6-mm/kernel/time/ntp.c
@@ -45,7 +45,6 @@ long time_maxerror = NTP_PHASE_LIMIT;	/*
 long time_esterror = NTP_PHASE_LIMIT;	/* estimated error (us)		*/
 long time_freq = (((NSEC_PER_SEC + HZ/2) % HZ - HZ/2) << SHIFT_USEC) / NSEC_PER_USEC;
 					/* frequency offset (scaled ppm)*/
-static long time_adj;			/* tick adjust (scaled 1 / HZ)	*/
 long time_reftime;			/* time at last adjustment (s)	*/
 long time_adjust;
 long time_next_adjust;
@@ -90,7 +89,7 @@ void ntp_update_frequency(void)
  */
 void second_overflow(void)
 {
-	long ltemp;
+	long ltemp, time_adj;
 
 	/* Bump the maxerror field */
 	time_maxerror += time_tolerance >> SHIFT_USEC;
@@ -195,6 +194,7 @@ void second_overflow(void)
 	time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
 #endif
 	tick_length = tick_length_base;
+	tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - (SHIFT_SCALE - 10));
 }
 
 /*
@@ -251,11 +251,9 @@ u64 current_tick_length(void)
 	u64 ret;
 
 	/* calculate the finest interval NTP will allow.
-	 *    ie: nanosecond value shifted by (SHIFT_SCALE - 10)
 	 */
 	ret = tick_length;
 	ret += (u64)(adjtime_adjustment() * 1000) << TICK_LENGTH_SHIFT;
-	ret += (s64)time_adj << (TICK_LENGTH_SHIFT - (SHIFT_SCALE - 10));
 
 	return ret;
 }

--

[NTP 3/9] add time_freq to tick length

[zippel]

[-- Attachment #1: 0003-NTP-add-time_freq-to-tick-length.txt --]
[-- Type: text/plain, Size: 1852 bytes --]

This adds the frequency part to ntp_update_frequency().

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
---
 kernel/time/ntp.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

Index: linux-2.6-mm/kernel/time/ntp.c
===================================================================
--- linux-2.6-mm.orig/kernel/time/ntp.c
+++ linux-2.6-mm/kernel/time/ntp.c
@@ -43,8 +43,7 @@ long time_tolerance = MAXFREQ;		/* frequ
 long time_precision = 1;		/* clock precision (us)		*/
 long time_maxerror = NTP_PHASE_LIMIT;	/* maximum error (us)		*/
 long time_esterror = NTP_PHASE_LIMIT;	/* estimated error (us)		*/
-long time_freq = (((NSEC_PER_SEC + HZ/2) % HZ - HZ/2) << SHIFT_USEC) / NSEC_PER_USEC;
-					/* frequency offset (scaled ppm)*/
+long time_freq;				/* frequency offset (scaled ppm)*/
 long time_reftime;			/* time at last adjustment (s)	*/
 long time_adjust;
 long time_next_adjust;
@@ -73,6 +72,7 @@ void ntp_update_frequency(void)
 {
 	tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT;
 	tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
+	tick_length_base += ((s64)time_freq * NSEC_PER_USEC) << (TICK_LENGTH_SHIFT - SHIFT_USEC);
 
 	do_div(tick_length_base, HZ);
 
@@ -169,8 +169,6 @@ void second_overflow(void)
 	 * Compute the frequency estimate and additional phase adjustment due
 	 * to frequency error for the next second.
 	 */
-	ltemp = time_freq;
-	time_adj += shift_right(ltemp,(SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE));
 
 #if HZ == 100
 	/*
@@ -395,7 +393,7 @@ int do_adjtimex(struct timex *txc)
 	    if (txc->modes & ADJ_TICK)
 		tick_usec = txc->tick;
 
-	    if (txc->modes & ADJ_TICK)
+	    if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
 		    ntp_update_frequency();
 	} /* txc->modes */
 leave:	if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)

--

[NTP 4/9] prescale time_offset

[zippel]

[-- Attachment #1: 0004-NTP-prescale-time_offset.txt --]
[-- Type: text/plain, Size: 5586 bytes --]

This converts time_offset into a scaled per tick value. This avoids now
completely the crude compensation in second_overflow().

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
---
 include/linux/timex.h |    2 -
 kernel/time/ntp.c     |   64 ++++++++++++--------------------------------------
 2 files changed, 17 insertions(+), 49 deletions(-)

Index: linux-2.6-mm/include/linux/timex.h
===================================================================
--- linux-2.6-mm.orig/include/linux/timex.h
+++ linux-2.6-mm/include/linux/timex.h
@@ -90,7 +90,7 @@
  * FINENSEC is 1 ns in SHIFT_UPDATE units of the time_phase variable.
  */
 #define SHIFT_SCALE 22		/* phase scale (shift) */
-#define SHIFT_UPDATE (SHIFT_KG + MAXTC) /* time offset scale (shift) */
+#define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */
 #define SHIFT_USEC 16		/* frequency offset scale (shift) */
 #define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */
 
Index: linux-2.6-mm/kernel/time/ntp.c
===================================================================
--- linux-2.6-mm.orig/kernel/time/ntp.c
+++ linux-2.6-mm/kernel/time/ntp.c
@@ -37,7 +37,7 @@ int tickadj = 500/HZ ? : 1;		/* microsec
 /* TIME_ERROR prevents overwriting the CMOS clock */
 int time_state = TIME_OK;		/* clock synchronization status	*/
 int time_status = STA_UNSYNC;		/* clock status bits		*/
-long time_offset;			/* time adjustment (us)		*/
+long time_offset;			/* time adjustment (ns)		*/
 long time_constant = 2;			/* pll time constant		*/
 long time_tolerance = MAXFREQ;		/* frequency tolerance (ppm)	*/
 long time_precision = 1;		/* clock precision (us)		*/
@@ -63,6 +63,7 @@ void ntp_clear(void)
 	ntp_update_frequency();
 
 	tick_length = tick_length_base;
+	time_offset = 0;
 }
 
 #define CLOCK_TICK_OVERFLOW	(LATCH * HZ - CLOCK_TICK_RATE)
@@ -89,7 +90,7 @@ void ntp_update_frequency(void)
  */
 void second_overflow(void)
 {
-	long ltemp, time_adj;
+	long time_adj;
 
 	/* Bump the maxerror field */
 	time_maxerror += time_tolerance >> SHIFT_USEC;
@@ -157,42 +158,14 @@ void second_overflow(void)
 	 * adjustment for each second is clamped so as to spread the adjustment
 	 * over not more than the number of seconds between updates.
 	 */
-	ltemp = time_offset;
-	if (!(time_status & STA_FLL))
-		ltemp = shift_right(ltemp, SHIFT_KG + time_constant);
-	ltemp = min(ltemp, (MAXPHASE / MINSEC) << SHIFT_UPDATE);
-	ltemp = max(ltemp, -(MAXPHASE / MINSEC) << SHIFT_UPDATE);
-	time_offset -= ltemp;
-	time_adj = ltemp << (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
-
-	/*
-	 * Compute the frequency estimate and additional phase adjustment due
-	 * to frequency error for the next second.
-	 */
-
-#if HZ == 100
-	/*
-	 * Compensate for (HZ==100) != (1 << SHIFT_HZ).  Add 25% and 3.125% to
-	 * get 128.125; => only 0.125% error (p. 14)
-	 */
-	time_adj += shift_right(time_adj, 2) + shift_right(time_adj, 5);
-#endif
-#if HZ == 250
-	/*
-	 * Compensate for (HZ==250) != (1 << SHIFT_HZ).  Add 1.5625% and
-	 * 0.78125% to get 255.85938; => only 0.05% error (p. 14)
-	 */
-	time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
-#endif
-#if HZ == 1000
-	/*
-	 * Compensate for (HZ==1000) != (1 << SHIFT_HZ).  Add 1.5625% and
-	 * 0.78125% to get 1023.4375; => only 0.05% error (p. 14)
-	 */
-	time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
-#endif
 	tick_length = tick_length_base;
-	tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - (SHIFT_SCALE - 10));
+	time_adj = time_offset;
+	if (!(time_status & STA_FLL))
+		time_adj = shift_right(time_adj, SHIFT_KG + time_constant);
+	time_adj = min(time_adj, -((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
+	time_adj = max(time_adj, ((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
+	time_offset -= time_adj;
+	tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE);
 }
 
 /*
@@ -353,12 +326,8 @@ int do_adjtimex(struct timex *txc)
 		     * Scale the phase adjustment and
 		     * clamp to the operating range.
 		     */
-		    if (ltemp > MAXPHASE)
-		        time_offset = MAXPHASE << SHIFT_UPDATE;
-		    else if (ltemp < -MAXPHASE)
-			time_offset = -(MAXPHASE << SHIFT_UPDATE);
-		    else
-		        time_offset = ltemp << SHIFT_UPDATE;
+		    time_offset = min(ltemp, MAXPHASE);
+		    time_offset = max(time_offset, -MAXPHASE);
 
 		    /*
 		     * Select whether the frequency is to be controlled
@@ -372,8 +341,7 @@ int do_adjtimex(struct timex *txc)
 		    time_reftime = xtime.tv_sec;
 		    if (time_status & STA_FLL) {
 		        if (mtemp >= MINSEC) {
-			    ltemp = (time_offset / mtemp) << (SHIFT_USEC -
-							      SHIFT_UPDATE);
+			    ltemp = ((time_offset << 12) / mtemp) << (SHIFT_USEC - 12);
 			    time_freq += shift_right(ltemp, SHIFT_KH);
 			} else /* calibration interval too short (p. 12) */
 				result = TIME_ERROR;
@@ -388,6 +356,7 @@ int do_adjtimex(struct timex *txc)
 		    }
 		    time_freq = min(time_freq, time_tolerance);
 		    time_freq = max(time_freq, -time_tolerance);
+		    time_offset = (time_offset * NSEC_PER_USEC / HZ) << SHIFT_UPDATE;
 		} /* STA_PLL */
 	    } /* txc->modes & ADJ_OFFSET */
 	    if (txc->modes & ADJ_TICK)
@@ -401,9 +370,8 @@ leave:	if ((time_status & (STA_UNSYNC|ST
 
 	if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
 	    txc->offset	   = save_adjust;
-	else {
-	    txc->offset = shift_right(time_offset, SHIFT_UPDATE);
-	}
+	else
+	    txc->offset    = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000;
 	txc->freq	   = time_freq;
 	txc->maxerror	   = time_maxerror;
 	txc->esterror	   = time_esterror;

--

[NTP 5/9] add time_adjust to tick length

[zippel]

[-- Attachment #1: 0005-NTP-add-time_adjust-to-tick-length.txt --]
[-- Type: text/plain, Size: 5207 bytes --]

This folds update_ntp_one_tick() into second_overflow() and adds
time_adjust to the tick length, this makes time_next_adjust unnecessary.
This slightly changes the adjtime() behaviour, instead of applying it to
the next tick, it's applied to the next second.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
---
 include/linux/timex.h |    1 
 kernel/time/ntp.c     |   71 ++++++++++++--------------------------------------
 kernel/timer.c        |    2 -
 3 files changed, 18 insertions(+), 56 deletions(-)

Index: linux-2.6-mm/include/linux/timex.h
===================================================================
--- linux-2.6-mm.orig/include/linux/timex.h
+++ linux-2.6-mm/include/linux/timex.h
@@ -216,7 +216,6 @@ extern long time_freq;		/* frequency off
 extern long time_reftime;	/* time at last adjustment (s) */
 
 extern long time_adjust;	/* The amount of adjtime left */
-extern long time_next_adjust;	/* Value for time_adjust at next tick */
 
 extern void ntp_clear(void);
 extern void ntp_update_frequency(void);
Index: linux-2.6-mm/kernel/time/ntp.c
===================================================================
--- linux-2.6-mm.orig/kernel/time/ntp.c
+++ linux-2.6-mm/kernel/time/ntp.c
@@ -28,8 +28,9 @@ unsigned long tick_usec = TICK_USEC; 		/
 unsigned long tick_nsec;			/* ACTHZ period (nsec) */
 static u64 tick_length, tick_length_base;
 
-/* Don't completely fail for HZ > 500.  */
-int tickadj = 500/HZ ? : 1;		/* microsecs */
+#define MAX_TICKADJ		500		/* microsecs */
+#define MAX_TICKADJ_SCALED	(((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \
+				  TICK_LENGTH_SHIFT) / HZ)
 
 /*
  * phase-lock loop variables
@@ -46,7 +47,6 @@ long time_esterror = NTP_PHASE_LIMIT;	/*
 long time_freq;				/* frequency offset (scaled ppm)*/
 long time_reftime;			/* time at last adjustment (s)	*/
 long time_adjust;
-long time_next_adjust;
 
 /**
  * ntp_clear - Clears the NTP state variables
@@ -166,46 +166,19 @@ void second_overflow(void)
 	time_adj = max(time_adj, ((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
 	time_offset -= time_adj;
 	tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE);
-}
-
-/*
- * Returns how many microseconds we need to add to xtime this tick
- * in doing an adjustment requested with adjtime.
- */
-static long adjtime_adjustment(void)
-{
-	long time_adjust_step;
-
-	time_adjust_step = time_adjust;
-	if (time_adjust_step) {
-		/*
-		 * We are doing an adjtime thing.  Prepare time_adjust_step to
-		 * be within bounds.  Note that a positive time_adjust means we
-		 * want the clock to run faster.
-		 *
-		 * Limit the amount of the step to be in the range
-		 * -tickadj .. +tickadj
-		 */
-		time_adjust_step = min(time_adjust_step, (long)tickadj);
-		time_adjust_step = max(time_adjust_step, (long)-tickadj);
-	}
-	return time_adjust_step;
-}
-
-/* in the NTP reference this is called "hardclock()" */
-void update_ntp_one_tick(void)
-{
-	long time_adjust_step;
 
-	time_adjust_step = adjtime_adjustment();
-	if (time_adjust_step)
-		/* Reduce by this step the amount of time left  */
-		time_adjust -= time_adjust_step;
-
-	/* Changes by adjtime() do not take effect till next tick. */
-	if (time_next_adjust != 0) {
-		time_adjust = time_next_adjust;
-		time_next_adjust = 0;
+	if (unlikely(time_adjust)) {
+		if (time_adjust > MAX_TICKADJ) {
+			time_adjust -= MAX_TICKADJ;
+			tick_length += MAX_TICKADJ_SCALED;
+		} else if (time_adjust < -MAX_TICKADJ) {
+			time_adjust += MAX_TICKADJ;
+			tick_length -= MAX_TICKADJ_SCALED;
+		} else {
+			time_adjust = 0;
+			tick_length += (s64)(time_adjust * NSEC_PER_USEC /
+					     HZ) << TICK_LENGTH_SHIFT;
+		}
 	}
 }
 
@@ -219,14 +192,7 @@ void update_ntp_one_tick(void)
  */
 u64 current_tick_length(void)
 {
-	u64 ret;
-
-	/* calculate the finest interval NTP will allow.
-	 */
-	ret = tick_length;
-	ret += (u64)(adjtime_adjustment() * 1000) << TICK_LENGTH_SHIFT;
-
-	return ret;
+	return tick_length;
 }
 
 
@@ -269,7 +235,7 @@ int do_adjtimex(struct timex *txc)
 	result = time_state;	/* mostly `TIME_OK' */
 
 	/* Save for later - semantics of adjtime is to return old value */
-	save_adjust = time_next_adjust ? time_next_adjust : time_adjust;
+	save_adjust = time_adjust;
 
 #if 0	/* STA_CLOCKERR is never set yet */
 	time_status &= ~STA_CLOCKERR;		/* reset STA_CLOCKERR */
@@ -316,8 +282,7 @@ int do_adjtimex(struct timex *txc)
 	    if (txc->modes & ADJ_OFFSET) {	/* values checked earlier */
 		if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
 		    /* adjtime() is independent from ntp_adjtime() */
-		    if ((time_next_adjust = txc->offset) == 0)
-			 time_adjust = 0;
+		    time_adjust = txc->offset;
 		}
 		else if (time_status & STA_PLL) {
 		    ltemp = txc->offset;
Index: linux-2.6-mm/kernel/timer.c
===================================================================
--- linux-2.6-mm.orig/kernel/timer.c
+++ linux-2.6-mm/kernel/timer.c
@@ -943,8 +943,6 @@ static void update_wall_time(void)
 		/* interpolator bits */
 		time_interpolator_update(clock->xtime_interval
 						>> clock->shift);
-		/* increment the NTP state machine */
-		update_ntp_one_tick();
 
 		/* accumulate error between NTP and clock interval */
 		clock->error += current_tick_length();

--

[NTP 6/9] remove time_tolerance

[zippel]

[-- Attachment #1: 0006-NTP-remove-time_tolerance.txt --]
[-- Type: text/plain, Size: 2694 bytes --]

time_tolerance isn't changed at all in the kernel, so simply remove it,
this simplifies the next patch, as it avoids a number of conversions.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
---
 include/linux/timex.h |    1 -
 kernel/time/ntp.c     |    9 ++++-----
 2 files changed, 4 insertions(+), 6 deletions(-)

Index: linux-2.6-mm/include/linux/timex.h
===================================================================
--- linux-2.6-mm.orig/include/linux/timex.h
+++ linux-2.6-mm/include/linux/timex.h
@@ -207,7 +207,6 @@ extern int time_state;		/* clock status 
 extern int time_status;		/* clock synchronization status bits */
 extern long time_offset;	/* time adjustment (us) */
 extern long time_constant;	/* pll time constant */
-extern long time_tolerance;	/* frequency tolerance (ppm) */
 extern long time_precision;	/* clock precision (us) */
 extern long time_maxerror;	/* maximum error */
 extern long time_esterror;	/* estimated error */
Index: linux-2.6-mm/kernel/time/ntp.c
===================================================================
--- linux-2.6-mm.orig/kernel/time/ntp.c
+++ linux-2.6-mm/kernel/time/ntp.c
@@ -40,7 +40,6 @@ int time_state = TIME_OK;		/* clock sync
 int time_status = STA_UNSYNC;		/* clock status bits		*/
 long time_offset;			/* time adjustment (ns)		*/
 long time_constant = 2;			/* pll time constant		*/
-long time_tolerance = MAXFREQ;		/* frequency tolerance (ppm)	*/
 long time_precision = 1;		/* clock precision (us)		*/
 long time_maxerror = NTP_PHASE_LIMIT;	/* maximum error (us)		*/
 long time_esterror = NTP_PHASE_LIMIT;	/* estimated error (us)		*/
@@ -93,7 +92,7 @@ void second_overflow(void)
 	long time_adj;
 
 	/* Bump the maxerror field */
-	time_maxerror += time_tolerance >> SHIFT_USEC;
+	time_maxerror += MAXFREQ >> SHIFT_USEC;
 	if (time_maxerror > NTP_PHASE_LIMIT) {
 		time_maxerror = NTP_PHASE_LIMIT;
 		time_status |= STA_UNSYNC;
@@ -319,8 +318,8 @@ int do_adjtimex(struct timex *txc)
 			} else /* calibration interval too long (p. 12) */
 				result = TIME_ERROR;
 		    }
-		    time_freq = min(time_freq, time_tolerance);
-		    time_freq = max(time_freq, -time_tolerance);
+		    time_freq = min(time_freq, MAXFREQ);
+		    time_freq = max(time_freq, -MAXFREQ);
 		    time_offset = (time_offset * NSEC_PER_USEC / HZ) << SHIFT_UPDATE;
 		} /* STA_PLL */
 	    } /* txc->modes & ADJ_OFFSET */
@@ -343,7 +342,7 @@ leave:	if ((time_status & (STA_UNSYNC|ST
 	txc->status	   = time_status;
 	txc->constant	   = time_constant;
 	txc->precision	   = time_precision;
-	txc->tolerance	   = time_tolerance;
+	txc->tolerance	   = MAXFREQ;
 	txc->tick	   = tick_usec;
 
 	/* PPS is not implemented, so these are zero */

--

[NTP 7/9] convert time_freq to nsec value

[zippel]

[-- Attachment #1: 0007-NTP-convert-time_freq-to-nsec-value.txt --]
[-- Type: text/plain, Size: 4982 bytes --]

This converts time_freq to a scaled nsec value and adds around 6bit of
extra resolution. This pushes the time_freq to its 32bit limits so the
calculatons have to be done with 64bit.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
---
 include/linux/timex.h |    2 ++
 kernel/time/ntp.c     |   36 ++++++++++++++++++++++--------------
 2 files changed, 24 insertions(+), 14 deletions(-)

Index: linux-2.6-mm/include/linux/timex.h
===================================================================
--- linux-2.6-mm.orig/include/linux/timex.h
+++ linux-2.6-mm/include/linux/timex.h
@@ -92,10 +92,12 @@
 #define SHIFT_SCALE 22		/* phase scale (shift) */
 #define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */
 #define SHIFT_USEC 16		/* frequency offset scale (shift) */
+#define SHIFT_NSEC 12		/* kernel frequency offset scale */
 #define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */
 
 #define MAXPHASE 512000L        /* max phase error (us) */
 #define MAXFREQ (512L << SHIFT_USEC)  /* max frequency error (ppm) */
+#define MAXFREQ_NSEC (512000L << SHIFT_NSEC) /* max frequency error (ppb) */
 #define MINSEC 16L              /* min interval between updates (s) */
 #define MAXSEC 1200L            /* max interval between updates (s) */
 #define	NTP_PHASE_LIMIT	(MAXPHASE << 5)	/* beyond max. dispersion */
Index: linux-2.6-mm/kernel/time/ntp.c
===================================================================
--- linux-2.6-mm.orig/kernel/time/ntp.c
+++ linux-2.6-mm/kernel/time/ntp.c
@@ -72,7 +72,7 @@ void ntp_update_frequency(void)
 {
 	tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT;
 	tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
-	tick_length_base += ((s64)time_freq * NSEC_PER_USEC) << (TICK_LENGTH_SHIFT - SHIFT_USEC);
+	tick_length_base += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
 
 	do_div(tick_length_base, HZ);
 
@@ -206,6 +206,7 @@ void __attribute__ ((weak)) notify_arch_
 int do_adjtimex(struct timex *txc)
 {
 	long ltemp, mtemp, save_adjust;
+	s64 freq_adj;
 	int result;
 
 	/* In order to modify anything, you gotta be super-user! */
@@ -251,7 +252,7 @@ int do_adjtimex(struct timex *txc)
 		    result = -EINVAL;
 		    goto leave;
 		}
-		time_freq = txc->freq;
+		time_freq = ((s64)txc->freq * NSEC_PER_USEC) >> (SHIFT_USEC - SHIFT_NSEC);
 	    }
 
 	    if (txc->modes & ADJ_MAXERROR) {
@@ -284,14 +285,14 @@ int do_adjtimex(struct timex *txc)
 		    time_adjust = txc->offset;
 		}
 		else if (time_status & STA_PLL) {
-		    ltemp = txc->offset;
+		    ltemp = txc->offset * NSEC_PER_USEC;
 
 		    /*
 		     * Scale the phase adjustment and
 		     * clamp to the operating range.
 		     */
-		    time_offset = min(ltemp, MAXPHASE);
-		    time_offset = max(time_offset, -MAXPHASE);
+		    time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC);
+		    time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC);
 
 		    /*
 		     * Select whether the frequency is to be controlled
@@ -303,24 +304,31 @@ int do_adjtimex(struct timex *txc)
 		        time_reftime = xtime.tv_sec;
 		    mtemp = xtime.tv_sec - time_reftime;
 		    time_reftime = xtime.tv_sec;
+		    freq_adj = 0;
 		    if (time_status & STA_FLL) {
 		        if (mtemp >= MINSEC) {
-			    ltemp = ((time_offset << 12) / mtemp) << (SHIFT_USEC - 12);
-			    time_freq += shift_right(ltemp, SHIFT_KH);
+			    freq_adj = (s64)time_offset << (SHIFT_NSEC - SHIFT_KH);
+			    if (time_offset < 0) {
+				freq_adj = -freq_adj;
+				do_div(freq_adj, mtemp);
+				freq_adj = -freq_adj;
+			    } else
+				do_div(freq_adj, mtemp);
 			} else /* calibration interval too short (p. 12) */
 				result = TIME_ERROR;
 		    } else {	/* PLL mode */
 		        if (mtemp < MAXSEC) {
-			    ltemp *= mtemp;
-			    time_freq += shift_right(ltemp,(time_constant +
+			    freq_adj = (s64)ltemp * mtemp;
+			    freq_adj = shift_right(freq_adj,(time_constant +
 						       time_constant +
-						       SHIFT_KF - SHIFT_USEC));
+						       SHIFT_KF - SHIFT_NSEC));
 			} else /* calibration interval too long (p. 12) */
 				result = TIME_ERROR;
 		    }
-		    time_freq = min(time_freq, MAXFREQ);
-		    time_freq = max(time_freq, -MAXFREQ);
-		    time_offset = (time_offset * NSEC_PER_USEC / HZ) << SHIFT_UPDATE;
+		    freq_adj += time_freq;
+		    freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
+		    time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
+		    time_offset = (time_offset / HZ) << SHIFT_UPDATE;
 		} /* STA_PLL */
 	    } /* txc->modes & ADJ_OFFSET */
 	    if (txc->modes & ADJ_TICK)
@@ -336,7 +344,7 @@ leave:	if ((time_status & (STA_UNSYNC|ST
 	    txc->offset	   = save_adjust;
 	else
 	    txc->offset    = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000;
-	txc->freq	   = time_freq;
+	txc->freq	   = (time_freq / NSEC_PER_USEC) << (SHIFT_USEC - SHIFT_NSEC);
 	txc->maxerror	   = time_maxerror;
 	txc->esterror	   = time_esterror;
 	txc->status	   = time_status;

--

[NTP 8/9] convert to the NTP4 reference model

[zippel]

[-- Attachment #1: 0008-NTP-convert-to-the-NTP4-reference-model.txt --]
[-- Type: text/plain, Size: 4974 bytes --]

This converts the kernel ntp model into a model which matches the
nanokernel reference implementations. The previous patches already
increased the resolution and precision of the computations, so that this
conversion becomes quite simple.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
---
 include/linux/timex.h |   11 ++++------
 kernel/time/ntp.c     |   51 ++++++++++++++++++--------------------------------
 2 files changed, 24 insertions(+), 38 deletions(-)

Index: linux-2.6-mm/include/linux/timex.h
===================================================================
--- linux-2.6-mm.orig/include/linux/timex.h
+++ linux-2.6-mm/include/linux/timex.h
@@ -70,10 +70,9 @@
  * zero to MAXTC, the PLL will converge in 15 minutes to 16 hours,
  * respectively.
  */
-#define SHIFT_KG 6		/* phase factor (shift) */
-#define SHIFT_KF 16		/* PLL frequency factor (shift) */
-#define SHIFT_KH 2		/* FLL frequency factor (shift) */
-#define MAXTC 6			/* maximum time constant (shift) */
+#define SHIFT_PLL	4	/* PLL frequency factor (shift) */
+#define SHIFT_FLL	2	/* FLL frequency factor (shift) */
+#define MAXTC		10	/* maximum time constant (shift) */
 
 /*
  * The SHIFT_SCALE define establishes the decimal point of the time_phase
@@ -98,8 +97,8 @@
 #define MAXPHASE 512000L        /* max phase error (us) */
 #define MAXFREQ (512L << SHIFT_USEC)  /* max frequency error (ppm) */
 #define MAXFREQ_NSEC (512000L << SHIFT_NSEC) /* max frequency error (ppb) */
-#define MINSEC 16L              /* min interval between updates (s) */
-#define MAXSEC 1200L            /* max interval between updates (s) */
+#define MINSEC 256		/* min interval between updates (s) */
+#define MAXSEC 2048		/* max interval between updates (s) */
 #define	NTP_PHASE_LIMIT	(MAXPHASE << 5)	/* beyond max. dispersion */
 
 /*
Index: linux-2.6-mm/kernel/time/ntp.c
===================================================================
--- linux-2.6-mm.orig/kernel/time/ntp.c
+++ linux-2.6-mm/kernel/time/ntp.c
@@ -151,18 +151,11 @@ void second_overflow(void)
 	}
 
 	/*
-	 * Compute the phase adjustment for the next second. In PLL mode, the
-	 * offset is reduced by a fixed factor times the time constant. In FLL
-	 * mode the offset is used directly. In either mode, the maximum phase
-	 * adjustment for each second is clamped so as to spread the adjustment
-	 * over not more than the number of seconds between updates.
+	 * Compute the phase adjustment for the next second. The offset is
+	 * reduced by a fixed factor times the time constant.
 	 */
 	tick_length = tick_length_base;
-	time_adj = time_offset;
-	if (!(time_status & STA_FLL))
-		time_adj = shift_right(time_adj, SHIFT_KG + time_constant);
-	time_adj = min(time_adj, -((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
-	time_adj = max(time_adj, ((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
+	time_adj = shift_right(time_offset, SHIFT_PLL + time_constant);
 	time_offset -= time_adj;
 	tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE);
 
@@ -206,7 +199,7 @@ void __attribute__ ((weak)) notify_arch_
 int do_adjtimex(struct timex *txc)
 {
 	long ltemp, mtemp, save_adjust;
-	s64 freq_adj;
+	s64 freq_adj, temp64;
 	int result;
 
 	/* In order to modify anything, you gotta be super-user! */
@@ -276,7 +269,7 @@ int do_adjtimex(struct timex *txc)
 		    result = -EINVAL;
 		    goto leave;
 		}
-		time_constant = txc->constant;
+		time_constant = min(txc->constant + 4, (long)MAXTC);
 	    }
 
 	    if (txc->modes & ADJ_OFFSET) {	/* values checked earlier */
@@ -304,26 +297,20 @@ int do_adjtimex(struct timex *txc)
 		        time_reftime = xtime.tv_sec;
 		    mtemp = xtime.tv_sec - time_reftime;
 		    time_reftime = xtime.tv_sec;
-		    freq_adj = 0;
-		    if (time_status & STA_FLL) {
-		        if (mtemp >= MINSEC) {
-			    freq_adj = (s64)time_offset << (SHIFT_NSEC - SHIFT_KH);
-			    if (time_offset < 0) {
-				freq_adj = -freq_adj;
-				do_div(freq_adj, mtemp);
-				freq_adj = -freq_adj;
-			    } else
-				do_div(freq_adj, mtemp);
-			} else /* calibration interval too short (p. 12) */
-				result = TIME_ERROR;
-		    } else {	/* PLL mode */
-		        if (mtemp < MAXSEC) {
-			    freq_adj = (s64)ltemp * mtemp;
-			    freq_adj = shift_right(freq_adj,(time_constant +
-						       time_constant +
-						       SHIFT_KF - SHIFT_NSEC));
-			} else /* calibration interval too long (p. 12) */
-				result = TIME_ERROR;
+
+		    freq_adj = (s64)time_offset * mtemp;
+		    freq_adj = shift_right(freq_adj, time_constant * 2 +
+					   (SHIFT_PLL + 2) * 2 - SHIFT_NSEC);
+		    if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
+			temp64 = (s64)time_offset << (SHIFT_NSEC - SHIFT_FLL);
+			if (time_offset < 0) {
+			    temp64 = -temp64;
+			    do_div(temp64, mtemp);
+			    freq_adj -= temp64;
+			} else {
+			    do_div(temp64, mtemp);
+			    freq_adj += temp64;
+			}
 		    }
 		    freq_adj += time_freq;
 		    freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);

--

[NTP 9/9] cleanup defines and comments

[zippel]

[-- Attachment #1: 0009-NTP-cleanup-defines-and-comments.txt --]
[-- Type: text/plain, Size: 4284 bytes --]

Remove a few unused defines and remove obsolete information from comments.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
---
 include/asm-frv/timex.h    |    5 -----
 include/asm-m32r/timex.h   |    3 ---
 include/asm-sh64/timex.h   |    3 ---
 include/asm-xtensa/timex.h |    3 ---
 include/linux/timex.h      |   13 +++----------
 5 files changed, 3 insertions(+), 24 deletions(-)

diff --git a/include/asm-frv/timex.h b/include/asm-frv/timex.h
index 2aa562f..a89bdde 100644
--- a/include/asm-frv/timex.h
+++ b/include/asm-frv/timex.h
@@ -6,11 +6,6 @@ #define _ASM_TIMEX_H
 #define CLOCK_TICK_RATE		1193180 /* Underlying HZ */
 #define CLOCK_TICK_FACTOR	20	/* Factor of both 1000000 and CLOCK_TICK_RATE */
 
-#define FINETUNE							\
-((((((long)LATCH * HZ - CLOCK_TICK_RATE) << SHIFT_HZ) *			\
-   (1000000/CLOCK_TICK_FACTOR) / (CLOCK_TICK_RATE/CLOCK_TICK_FACTOR))	\
-  << (SHIFT_SCALE-SHIFT_HZ)) / HZ)
-
 typedef unsigned long cycles_t;
 
 static inline cycles_t get_cycles(void)
diff --git a/include/asm-m32r/timex.h b/include/asm-m32r/timex.h
index e89bfd1..019441c 100644
--- a/include/asm-m32r/timex.h
+++ b/include/asm-m32r/timex.h
@@ -12,9 +12,6 @@ #define _ASM_M32R_TIMEX_H
 
 #define CLOCK_TICK_RATE	(CONFIG_BUS_CLOCK / CONFIG_TIMER_DIVIDE)
 #define CLOCK_TICK_FACTOR	20	/* Factor of both 1000000 and CLOCK_TICK_RATE */
-#define FINETUNE ((((((long)LATCH * HZ - CLOCK_TICK_RATE) << SHIFT_HZ) * \
-	(1000000/CLOCK_TICK_FACTOR) / (CLOCK_TICK_RATE/CLOCK_TICK_FACTOR)) \
-		<< (SHIFT_SCALE-SHIFT_HZ)) / HZ)
 
 #ifdef __KERNEL__
 /*
diff --git a/include/asm-sh64/timex.h b/include/asm-sh64/timex.h
index af0b792..163e2b6 100644
--- a/include/asm-sh64/timex.h
+++ b/include/asm-sh64/timex.h
@@ -17,9 +17,6 @@ #define __ASM_SH64_TIMEX_H
 
 #define CLOCK_TICK_RATE	1193180 /* Underlying HZ */
 #define CLOCK_TICK_FACTOR	20	/* Factor of both 1000000 and CLOCK_TICK_RATE */
-#define FINETUNE ((((((long)LATCH * HZ - CLOCK_TICK_RATE) << SHIFT_HZ) * \
-	(1000000/CLOCK_TICK_FACTOR) / (CLOCK_TICK_RATE/CLOCK_TICK_FACTOR)) \
-		<< (SHIFT_SCALE-SHIFT_HZ)) / HZ)
 
 typedef unsigned long cycles_t;
 
diff --git a/include/asm-xtensa/timex.h b/include/asm-xtensa/timex.h
index d14a375..c7b705e 100644
--- a/include/asm-xtensa/timex.h
+++ b/include/asm-xtensa/timex.h
@@ -31,9 +31,6 @@ #define LINUX_TIMER_MASK        (1L << L
 
 #define CLOCK_TICK_RATE 	1193180	/* (everyone is using this value) */
 #define CLOCK_TICK_FACTOR       20 /* Factor of both 10^6 and CLOCK_TICK_RATE */
-#define FINETUNE ((((((long)LATCH * HZ - CLOCK_TICK_RATE) << SHIFT_HZ) * \
-	(1000000/CLOCK_TICK_FACTOR) / (CLOCK_TICK_RATE/CLOCK_TICK_FACTOR)) \
-		<< (SHIFT_SCALE-SHIFT_HZ)) / HZ)
 
 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
 extern unsigned long ccount_per_jiffy;
diff --git a/include/linux/timex.h b/include/linux/timex.h
index 9879e3c..0b2e1b5 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -75,24 +75,17 @@ #define SHIFT_FLL	2	/* FLL frequency fac
 #define MAXTC		10	/* maximum time constant (shift) */
 
 /*
- * The SHIFT_SCALE define establishes the decimal point of the time_phase
- * variable which serves as an extension to the low-order bits of the
- * system clock variable. The SHIFT_UPDATE define establishes the decimal
- * point of the time_offset variable which represents the current offset
- * with respect to standard time. The FINENSEC define represents 1 nsec in
- * scaled units.
+ * The SHIFT_UPDATE define establishes the decimal point of the
+ * time_offset variable which represents the current offset with
+ * respect to standard time.
  *
  * SHIFT_USEC defines the scaling (shift) of the time_freq and
  * time_tolerance variables, which represent the current frequency
  * offset and maximum frequency tolerance.
- *
- * FINENSEC is 1 ns in SHIFT_UPDATE units of the time_phase variable.
  */
-#define SHIFT_SCALE 22		/* phase scale (shift) */
 #define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */
 #define SHIFT_USEC 16		/* frequency offset scale (shift) */
 #define SHIFT_NSEC 12		/* kernel frequency offset scale */
-#define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */
 
 #define MAXPHASE 512000L        /* max phase error (us) */
 #define MAXFREQ (512L << SHIFT_USEC)  /* max frequency error (ppm) */
-- 
1.4.1

--

Re: [NTP 8/9] convert to the NTP4 reference model

[Andrew Morton]

On Thu, 10 Aug 2006 02:01:54 +0200
zippel@linux-m68k.org wrote:

> This converts the kernel ntp model into a model which matches the
> nanokernel reference implementations.

For the ntp ignorami amongst us...  what is a "nanokernel reference
implementation" and why do we want one?

Thanks.

Re: [NTP 8/9] convert to the NTP4 reference model

[Roman Zippel]

Hi,

On Thu, 10 Aug 2006, Andrew Morton wrote:

> > This converts the kernel ntp model into a model which matches the
> > nanokernel reference implementations.
> 
> For the ntp ignorami amongst us...  what is a "nanokernel reference
> implementation" and why do we want one?

It's the behaviour the current ntp daemon expects, the ntp documentation 
has more information and a link to the package (e.g. under Debian at 
/usr/share/doc/ntp-doc/html/kern.html).

bye, Roman

Re: [NTP 8/9] convert to the NTP4 reference model

[Andrew Morton]

On Thu, 10 Aug 2006 21:14:00 +0200 (CEST)
Roman Zippel <zippel@linux-m68k.org> wrote:

> Hi,
> 
> On Thu, 10 Aug 2006, Andrew Morton wrote:
> 
> > > This converts the kernel ntp model into a model which matches the
> > > nanokernel reference implementations.
> > 
> > For the ntp ignorami amongst us...  what is a "nanokernel reference
> > implementation" and why do we want one?
> 
> It's the behaviour the current ntp daemon expects, the ntp documentation 
> has more information and a link to the package (e.g. under Debian at 
> /usr/share/doc/ntp-doc/html/kern.html).
> 

So...  the current kernel is behaving in a manner other than that which the
NTP daemon expects?  Does this cause any problems?

I'm trying to work out what reason we might have for merging this patch.

Re: [NTP 8/9] convert to the NTP4 reference model

[Roman Zippel]

Hi,

On Thu, 10 Aug 2006, Andrew Morton wrote:

> > It's the behaviour the current ntp daemon expects, the ntp documentation 
> > has more information and a link to the package (e.g. under Debian at 
> > /usr/share/doc/ntp-doc/html/kern.html).
> > 
> 
> So...  the current kernel is behaving in a manner other than that which the
> NTP daemon expects?  Does this cause any problems?

It's not drastically different, so for normal internet usage there is no 
big difference.
http://www.ntp.org/ntpfaq/NTP-s-compat.htm has a bit more information on 
this topic.

> I'm trying to work out what reason we might have for merging this patch.

It also allows us to sanely readd the PPS bits, where the changes were 
more significant.

bye, Roman

Re: [NTP 0/9] NTP patches

[john stultz]

On Thu, 2006-08-10 at 02:01 +0200, zippel@linux-m68k.org wrote:
> Here is my current version of the NTP patches.
> They precalculate as much possible and get rid of a lot of rather crude
> compensation code. The tick length is now a much simpler value, updated
> once a second, which greatly reduces the dependency on HZ.
> I rebased the patches against current -mm + John's ntp.c patch.

Hey Roman,
	How much real-world testing have you done with these patches? I've been
running w/ this set of patches for a few days and I've been noticing my
system is having difficulties synching up w/ the NTP server.

I haven't been logging anything, so its currently uncertain data, but
normally I've seen NTP sync the time within 1-2ms in just an hour or so,
however since this morning (~6 hours ago) I'm seeing it still 10ms off.

I'm going to let it run for the rest of the day then try to bisect the
patches to see where things went wrong. I'll let you know as soon as I
find anything.

thanks
-john

Re: [NTP 0/9] NTP patches

[Roman Zippel]

Hi,

On Wed, 16 Aug 2006, john stultz wrote:

> 	How much real-world testing have you done with these patches? I've been
> running w/ this set of patches for a few days and I've been noticing my
> system is having difficulties synching up w/ the NTP server.

I tested it on a few machines of course.

> I haven't been logging anything, so its currently uncertain data, but
> normally I've seen NTP sync the time within 1-2ms in just an hour or so,
> however since this morning (~6 hours ago) I'm seeing it still 10ms off.
> 
> I'm going to let it run for the rest of the day then try to bisect the
> patches to see where things went wrong. I'll let you know as soon as I
> find anything.

I would need the loopstats over a few days to really say something about 
this. It may also depend on the stability of your remote NTP serer. The 
new code adjusts a little a slower, but should be overall a little more 
stable.
The ntpd does basically "if (!pll_nano) ntv.constant = sys_poll - 4;" to 
adjust for the difference in behaviour of the two models, but this causes 
rather fast adjustments. In the NTP4 patch I undo this adjustment for the 
new model.

> I'm going to let it run for the rest of the day then try to bisect the
> patches to see where things went wrong. I'll let you know as soon as I
> find anything.

Well, upto the NTP4 patch the behaviour should be mostly unchanged.

bye, Roman

Re: [NTP 5/9] add time_adjust to tick length

[Atsushi Nemoto]

On Thu, 10 Aug 2006 02:01:51 +0200, zippel@linux-m68k.org wrote:
> This folds update_ntp_one_tick() into second_overflow() and adds
> time_adjust to the tick length, this makes time_next_adjust unnecessary.
> This slightly changes the adjtime() behaviour, instead of applying it to
> the next tick, it's applied to the next second.
...
> -/* Don't completely fail for HZ > 500.  */
> -int tickadj = 500/HZ ? : 1;		/* microsecs */

The tickadj is used by cris, frv, m32r, m68k, mips and sparc.  This
patch would break build on those platforms.

I have not looked at this patch closely yet.  Just a report.
---
Atsushi Nemoto

Re: [NTP 5/9] add time_adjust to tick length

[Roman Zippel]

Hi,

On Mon, 21 Aug 2006, Atsushi Nemoto wrote:

> On Thu, 10 Aug 2006 02:01:51 +0200, zippel@linux-m68k.org wrote:
> > This folds update_ntp_one_tick() into second_overflow() and adds
> > time_adjust to the tick length, this makes time_next_adjust unnecessary.
> > This slightly changes the adjtime() behaviour, instead of applying it to
> > the next tick, it's applied to the next second.
> ...
> > -/* Don't completely fail for HZ > 500.  */
> > -int tickadj = 500/HZ ? : 1;		/* microsecs */
> 
> The tickadj is used by cris, frv, m32r, m68k, mips and sparc.  This
> patch would break build on those platforms.
> 
> I have not looked at this patch closely yet.  Just a report.

Oops, I indeed missed that. I searched for if anyone would change that 
value, but later forgot about the other users.
A simple solution would be to move this (constant) value to a header and 
another rather simple solution would be to remove it completely, as it's 
rather bogus anyway. These users check time_adjust, which is unused in a 
NTP controlled system. The correct value to check would be the tick 
length, but I'm sure it's really worth the trouble.

bye, Roman