From: Ingo Molnar <mingo@elte.hu>
Date: Sun, 22 Feb 2009 15:03:37 +0000 (+0100)
Subject: time: ntp: simplify ntp_tick_adj calculations
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=069569e025706f27f939785f86a94d5d8ce55dce;p=openwrt%2Fstaging%2Fblogic.git

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@elte.hu>
---

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 7447d57e021a..a3fe7ef2d83b 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;
 }