Author: Ingo Molnar <mingo@xxxxxxx>
AuthorDate: Sun, 22 Feb 2009 16:03:37 +0100
Commit: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 25 Feb 2009 18:38:16 +0100
time: ntp: simplify ntp_tick_adj calculations
Impact: micro-optimization
Convert the (internal) ntp_tick_adj value we store from unscaled
units to scaled units. This is a constant that we never modify,
so scaling it up once during bootup is enough - we dont have to
do it for every adjustment step.
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/time/ntp.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 7447d57..a3fe7ef 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -71,7 +71,8 @@ static long time_reftime;
long time_adjust;
-static long ntp_tick_adj;
+/* constant (boot-param configurable) NTP tick adjustment (upscaled) */
+static s64 ntp_tick_adj;
/*
* NTP methods:
@@ -89,7 +90,7 @@ static void ntp_update_frequency(void)
second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
<< NTP_SCALE_SHIFT;
- second_length += (s64)ntp_tick_adj << NTP_SCALE_SHIFT;
+ second_length += ntp_tick_adj;
second_length += time_freq;
tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
@@ -540,6 +541,8 @@ int do_adjtimex(struct timex *txc)
static int __init ntp_tick_adj_setup(char *str)
{
ntp_tick_adj = simple_strtol(str, NULL, 0);
+ ntp_tick_adj <<= NTP_SCALE_SHIFT;
+
return 1;
}
--
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