Messages in this thread Patch in this message | | | Subject | [RFC][PATCH - 12/12] NTP cleanup: use ppm instead of unit adj returned by ntp_advance | From | john stultz <> | Date | Fri, 15 Jul 2005 20:09:58 -0700 |
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All, This patch stops ntp_advance() from returning unit adjustments (ie: nanoseconds). Instead the update_wall_time() function uses the ppm adjustment from get_ntp_adjustment() which is then converted into a nanosecond adjustment value.
Any comments or feedback would be greatly appreciated.
thanks -john
linux-2.6.13-rc3_timeofday-ntp-part12_B4.patch ============================================ diff --git a/include/linux/ntp.h b/include/linux/ntp.h --- a/include/linux/ntp.h +++ b/include/linux/ntp.h @@ -9,8 +9,11 @@ #include <linux/time.h> #include <linux/timex.h> +/* Required to safely shift negative values */ +#define shiftR(x,s) (x < 0) ? (-((-x) >> (s))) : ((x) >> (s)) + /* NTP state machine interfaces */ -int ntp_advance(unsigned long interval_nsec); +void ntp_advance(unsigned long interval_nsec); int ntp_adjtimex(struct timex*); int ntp_leapsecond(struct timespec now); void ntp_clear(void); diff --git a/kernel/ntp.c b/kernel/ntp.c --- a/kernel/ntp.c +++ b/kernel/ntp.c @@ -3,7 +3,9 @@ * * NTP state machine and time scaling code. * -* Code moved from kernel/time.c and kernel/timer.c +* Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com) +* +* Code moved and rewritten from kernel/time.c and kernel/timer.c * Please see those files for original copyrights. * * This program is free software; you can redistribute it and/or modify @@ -48,8 +50,6 @@ /* Don't completely fail for HZ > 500. */ int tickadj = 500/HZ ? : 1; /* microsecs */ -static long time_phase; /* phase offset (scaled us) */ -static long time_adj; /* tick adjust (scaled 1 / HZ) */ /* Chapter 5: Kernel Variables [RFC 1589 pg. 28] */ /* 5.1 Interface Variables */ @@ -82,13 +82,9 @@ static seqlock_t ntp_lock = SEQLOCK_UNLO #define MAX_SINGLESHOT_ADJ 500 /* (ppm) */ #define SEC_PER_DAY 86400 -/* Required to safely shift negative values */ -#define shiftR(x,s) (x < 0) ? (-((-x) >> (s))) : ((x) >> (s)) - -int ntp_advance(unsigned long interval_nsec) +void ntp_advance(unsigned long interval_nsec) { static unsigned long interval_sum = 0; - long time_adjust_step, delta_nsec; unsigned long flags; static long ss_adj = 0; @@ -130,23 +126,6 @@ int ntp_advance(unsigned long interval_n ntp_offset -= next_adj; offset_adj = shiftR(next_adj, SHIFT_UPDATE); /* ppm */ - - time_adj = next_adj << (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE); - time_adj += shiftR(ntp_freq, (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE)); -#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 += shiftR(time_adj,2) + shiftR(time_adj,5); -#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 += shiftR(time_adj,6) + shiftR(time_adj,7); -#endif /* Set ss_adj for the next second */ ss_adj = min_t(unsigned long, singleshot_adj, MAX_SINGLESHOT_ADJ); singleshot_adj -= ss_adj; @@ -158,42 +137,6 @@ int ntp_advance(unsigned long interval_n shifted_ppm_sum += ntp_freq; /* already shifted by SHIFT_USEC */ shifted_ppm_sum += ss_adj << SHIFT_USEC; - - if ( (time_adjust_step = ntp_adjtime_offset) != 0 ) { - /* We are doing an adjtime thing. - * - * Prepare time_adjust_step to be within bounds. - * Note that a positive ntp_adjtime_offset means we want the clock - * to run faster. - * - * Limit the amount of the step to be in the range - * -tickadj .. +tickadj - */ - if (ntp_adjtime_offset > tickadj) - time_adjust_step = tickadj; - else if (ntp_adjtime_offset < -tickadj) - time_adjust_step = -tickadj; - - /* Reduce by this step the amount of time left */ - ntp_adjtime_offset -= time_adjust_step; - } - delta_nsec = time_adjust_step * 1000; - - /* - * Advance the phase, once it gets to one microsecond, then - * advance the tick more. - */ - time_phase += time_adj; - if (time_phase <= -FINENSEC) { - long ltemp = -time_phase >> (SHIFT_SCALE - 10); - time_phase += ltemp << (SHIFT_SCALE - 10); - delta_nsec -= ltemp; - } else if (time_phase >= FINENSEC) { - long ltemp = time_phase >> (SHIFT_SCALE - 10); - time_phase -= ltemp << (SHIFT_SCALE - 10); - delta_nsec += ltemp; - } - /* Changes by adjtime() do not take effect till next tick. */ if (ntp_next_adjtime_offset != 0) { ntp_adjtime_offset = ntp_next_adjtime_offset; @@ -201,7 +144,6 @@ int ntp_advance(unsigned long interval_n } write_sequnlock_irqrestore(&ntp_lock, flags); - return delta_nsec; } /** diff --git a/kernel/timer.c b/kernel/timer.c --- a/kernel/timer.c +++ b/kernel/timer.c @@ -598,17 +598,23 @@ struct timespec wall_to_monotonic __attr EXPORT_SYMBOL(xtime); - /* in the NTP reference this is called "hardclock()" */ static void update_wall_time_one_tick(void) { - long delta_nsec; + long delta_nsec, ppm; + unsigned long interval_nsec; + + interval_nsec = tick_nsec; + ppm = ntp_get_adjustment(); - delta_nsec = tick_nsec + ntp_advance(tick_nsec); + delta_nsec = interval_nsec; + delta_nsec += shiftR((interval_nsec * ppm),SHIFT_USEC)/1000000; xtime.tv_nsec += delta_nsec; - time_interpolator_update(delta_nsec); + ntp_advance(interval_nsec); + + time_interpolator_update(delta_nsec); } /*
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