[patch 03/46] [RFC] HZ free ntp

Thomas Gleixner
2007-01-23T22:17:09Z

[-- Attachment #1: ntp-make-dyntick-aware.patch --]
[-- Type: text/plain, Size: 5526 bytes --]

>From johnstul@us.ibm.com Wed Dec 20 02:36:15 2006

Distangle the NTP update from HZ. This is necessary for dynamic tick
enabled kernels.

---
include/linux/timex.h | 7 +++++++
kernel/hrtimer.c | 11 ++++++++---
kernel/time/ntp.c | 30 +++++++++++++++++++-----------
kernel/timer.c | 4 ++--
4 files changed, 36 insertions(+), 16 deletions(-)

Index: linux-2.6.20-rc4-mm1-bo/include/linux/timex.h
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/include/linux/timex.h
+++ linux-2.6.20-rc4-mm1-bo/include/linux/timex.h
@@ -286,6 +286,13 @@ static inline void time_interpolator_upd

#define TICK_LENGTH_SHIFT 32

+#ifdef CONFIG_NO_HZ
+#define NTP_INTERVAL_FREQ (2)
+#else
+#define NTP_INTERVAL_FREQ (HZ)
+#endif
+#define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)
+
/* Returns how long ticks are at present, in ns / 2^(SHIFT_SCALE-10). */
extern u64 current_tick_length(void);

Index: linux-2.6.20-rc4-mm1-bo/kernel/time/ntp.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/time/ntp.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/time/ntp.c
@@ -24,7 +24,7 @@ static u64 tick_length, tick_length_base

#define MAX_TICKADJ 500 /* microsecs */
#define MAX_TICKADJ_SCALED (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \
- TICK_LENGTH_SHIFT) / HZ)
+ TICK_LENGTH_SHIFT) / NTP_INTERVAL_FREQ)

/*
* phase-lock loop variables
@@ -46,13 +46,17 @@ long time_adjust;

static 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 << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
+ u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
+ << TICK_LENGTH_SHIFT;
+ second_length += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
+ second_length += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);

- do_div(tick_length_base, HZ);
+ tick_length_base = second_length;

- tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT;
+ do_div(second_length, HZ);
+ tick_nsec = second_length >> TICK_LENGTH_SHIFT;
+
+ do_div(tick_length_base, NTP_INTERVAL_FREQ);
}

/**
@@ -162,7 +166,7 @@ void second_overflow(void)
tick_length -= MAX_TICKADJ_SCALED;
} else {
tick_length += (s64)(time_adjust * NSEC_PER_USEC /
- HZ) << TICK_LENGTH_SHIFT;
+ NTP_INTERVAL_FREQ) << TICK_LENGTH_SHIFT;
time_adjust = 0;
}
}
@@ -239,7 +243,8 @@ int do_adjtimex(struct timex *txc)
result = -EINVAL;
goto leave;
}
- time_freq = ((s64)txc->freq * NSEC_PER_USEC) >> (SHIFT_USEC - SHIFT_NSEC);
+ time_freq = ((s64)txc->freq * NSEC_PER_USEC)
+ >> (SHIFT_USEC - SHIFT_NSEC);
}

if (txc->modes & ADJ_MAXERROR) {
@@ -309,7 +314,8 @@ int do_adjtimex(struct timex *txc)
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;
+ time_offset = (time_offset / NTP_INTERVAL_FREQ)
+ << SHIFT_UPDATE;
} /* STA_PLL */
} /* txc->modes & ADJ_OFFSET */
if (txc->modes & ADJ_TICK)
@@ -324,8 +330,10 @@ 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) * HZ / 1000;
- txc->freq = (time_freq / NSEC_PER_USEC) << (SHIFT_USEC - SHIFT_NSEC);
+ txc->offset = shift_right(time_offset, SHIFT_UPDATE)
+ * NTP_INTERVAL_FREQ / 1000;
+ txc->freq = (time_freq / NSEC_PER_USEC)
+ << (SHIFT_USEC - SHIFT_NSEC);
txc->maxerror = time_maxerror;
txc->esterror = time_esterror;
txc->status = time_status;
Index: linux-2.6.20-rc4-mm1-bo/kernel/timer.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/timer.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/timer.c
@@ -890,7 +890,7 @@ void __init timekeeping_init(void)
ntp_clear();

clock = clocksource_get_next();
- clocksource_calculate_interval(clock, tick_nsec);
+ clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
clock->cycle_last = clocksource_read(clock);

write_sequnlock_irqrestore(&xtime_lock, flags);
@@ -1092,7 +1092,7 @@ static void update_wall_time(void)
if (change_clocksource()) {
clock->error = 0;
clock->xtime_nsec = 0;
- clocksource_calculate_interval(clock, tick_nsec);
+ clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
}
}

Index: linux-2.6.20-rc4-mm1-bo/kernel/hrtimer.c
===================================================================
--- linux-2.6.20-rc4-mm1-bo.orig/kernel/hrtimer.c
+++ linux-2.6.20-rc4-mm1-bo/kernel/hrtimer.c
@@ -128,15 +128,20 @@ EXPORT_SYMBOL_GPL(ktime_get_ts);
static void hrtimer_get_softirq_time(struct hrtimer_base *base)
{
ktime_t xtim, tomono;
+ struct timespec xts;
unsigned long seq;

do {
seq = read_seqbegin(&xtime_lock);
- xtim = timespec_to_ktime(xtime);
- tomono = timespec_to_ktime(wall_to_monotonic);
-
+#ifdef CONFIG_NO_HZ
+ getnstimeofday(&xts);
+#else
+ xts = xtime;
+#endif
} while (read_seqretry(&xtime_lock, seq));

+ xtim = timespec_to_ktime(xts);
+ tomono = timespec_to_ktime(wall_to_monotonic);
base[CLOCK_REALTIME].softirq_time = xtim;
base[CLOCK_MONOTONIC].softirq_time = ktime_add(xtim, tomono);
}

--