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authorRoman Zippel <zippel@linux-m68k.org>2008-05-01 07:34:36 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-05-01 11:03:58 -0400
commit9f14f669d18477fe3df071e2fa4da36c00acee8e (patch)
tree84b5600017902ced77ee0cb9a4bc21a6768d22e5 /include
parent074b3b87941c99bc0ce35385b5817924b1ed0c23 (diff)
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 'include')
-rw-r--r--include/linux/timex.h9
1 files changed, 2 insertions, 7 deletions
diff --git a/include/linux/timex.h b/include/linux/timex.h
index 48c3376dce71..9fbdd12a52f1 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -76,27 +76,22 @@
76#define MAXTC 10 /* maximum time constant (shift) */ 76#define MAXTC 10 /* maximum time constant (shift) */
77 77
78/* 78/*
79 * The SHIFT_UPDATE define establishes the decimal point of the
80 * time_offset variable which represents the current offset with
81 * respect to standard time.
82 *
83 * SHIFT_USEC defines the scaling (shift) of the time_freq and 79 * SHIFT_USEC defines the scaling (shift) of the time_freq and
84 * time_tolerance variables, which represent the current frequency 80 * time_tolerance variables, which represent the current frequency
85 * offset and maximum frequency tolerance. 81 * offset and maximum frequency tolerance.
86 */ 82 */
87#define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */
88#define SHIFT_USEC 16 /* frequency offset scale (shift) */ 83#define SHIFT_USEC 16 /* frequency offset scale (shift) */
89#define PPM_SCALE (NSEC_PER_USEC << (TICK_LENGTH_SHIFT - SHIFT_USEC)) 84#define PPM_SCALE (NSEC_PER_USEC << (TICK_LENGTH_SHIFT - SHIFT_USEC))
90#define PPM_SCALE_INV_SHIFT 20 85#define PPM_SCALE_INV_SHIFT 20
91#define PPM_SCALE_INV ((1ll << (PPM_SCALE_INV_SHIFT + TICK_LENGTH_SHIFT)) / \ 86#define PPM_SCALE_INV ((1ll << (PPM_SCALE_INV_SHIFT + TICK_LENGTH_SHIFT)) / \
92 PPM_SCALE + 1) 87 PPM_SCALE + 1)
93 88
94#define MAXPHASE 512000L /* max phase error (us) */ 89#define MAXPHASE 500000000l /* max phase error (ns) */
95#define MAXFREQ 500000 /* max frequency error (ns/s) */ 90#define MAXFREQ 500000 /* max frequency error (ns/s) */
96#define MAXFREQ_SCALED ((s64)MAXFREQ << TICK_LENGTH_SHIFT) 91#define MAXFREQ_SCALED ((s64)MAXFREQ << TICK_LENGTH_SHIFT)
97#define MINSEC 256 /* min interval between updates (s) */ 92#define MINSEC 256 /* min interval between updates (s) */
98#define MAXSEC 2048 /* max interval between updates (s) */ 93#define MAXSEC 2048 /* max interval between updates (s) */
99#define NTP_PHASE_LIMIT (MAXPHASE << 5) /* beyond max. dispersion */ 94#define NTP_PHASE_LIMIT ((MAXPHASE / NSEC_PER_USEC) << 5) /* beyond max. dispersion */
100 95
101/* 96/*
102 * syscall interface - used (mainly by NTP daemon) 97 * syscall interface - used (mainly by NTP daemon)