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| author | Roman Zippel <zippel@linux-m68k.org> | 2008-05-01 04:34:36 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-05-01 08:03:58 -0700 |
| commit | 9f14f669d18477fe3df071e2fa4da36c00acee8e (patch) | |
| tree | 84b5600017902ced77ee0cb9a4bc21a6768d22e5 /kernel/time | |
| parent | 074b3b87941c99bc0ce35385b5817924b1ed0c23 (diff) | |
| download | linux-9f14f669d18477fe3df071e2fa4da36c00acee8e.tar.bz2 | |
ntp: increase time_offset resolution
time_offset is already a 64bit value but its resolution barely used, so this
makes better use of it by replacing SHIFT_UPDATE with TICK_LENGTH_SHIFT.
Side note: the SHIFT_HZ in SHIFT_UPDATE was incorrect for CONFIG_NO_HZ and the
primary reason for changing time_offset to 64bit to avoid the overflow.
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/ntp.c | 23 |
1 files changed, 11 insertions, 12 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index c6ae0c249891..44491de312a0 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -65,16 +65,15 @@ static void ntp_update_offset(long offset) if (!(time_status & STA_PLL)) return; - time_offset = offset; if (!(time_status & STA_NANO)) - time_offset *= NSEC_PER_USEC; + offset *= NSEC_PER_USEC; /* * Scale the phase adjustment and * clamp to the operating range. */ - time_offset = min(time_offset, (s64)MAXPHASE * NSEC_PER_USEC); - time_offset = max(time_offset, (s64)-MAXPHASE * NSEC_PER_USEC); + offset = min(offset, MAXPHASE); + offset = max(offset, -MAXPHASE); /* * Select how the frequency is to be controlled @@ -85,19 +84,19 @@ static void ntp_update_offset(long offset) mtemp = xtime.tv_sec - time_reftime; time_reftime = xtime.tv_sec; - freq_adj = time_offset * mtemp; + freq_adj = (s64)offset * mtemp; freq_adj <<= TICK_LENGTH_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant); time_status &= ~STA_MODE; if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { - freq_adj += div_s64(time_offset << (TICK_LENGTH_SHIFT - SHIFT_FLL), + freq_adj += div_s64((s64)offset << (TICK_LENGTH_SHIFT - SHIFT_FLL), mtemp); time_status |= STA_MODE; } freq_adj += time_freq; freq_adj = min(freq_adj, MAXFREQ_SCALED); time_freq = max(freq_adj, -MAXFREQ_SCALED); - time_offset = div_s64(time_offset, NTP_INTERVAL_FREQ); - time_offset <<= SHIFT_UPDATE; + + time_offset = div_s64((s64)offset << TICK_LENGTH_SHIFT, NTP_INTERVAL_FREQ); } /** @@ -128,7 +127,7 @@ void ntp_clear(void) */ void second_overflow(void) { - long time_adj; + s64 time_adj; /* Bump the maxerror field */ time_maxerror += MAXFREQ / NSEC_PER_USEC; @@ -184,7 +183,7 @@ void second_overflow(void) tick_length = tick_length_base; time_adj = shift_right(time_offset, SHIFT_PLL + time_constant); time_offset -= time_adj; - tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE); + tick_length += time_adj; if (unlikely(time_adjust)) { if (time_adjust > MAX_TICKADJ) { @@ -363,8 +362,8 @@ int do_adjtimex(struct timex *txc) (txc->modes == ADJ_OFFSET_SS_READ)) txc->offset = save_adjust; else { - txc->offset = ((long)shift_right(time_offset, SHIFT_UPDATE)) * - NTP_INTERVAL_FREQ; + txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, + TICK_LENGTH_SHIFT); if (!(time_status & STA_NANO)) txc->offset /= NSEC_PER_USEC; } |