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 7447d57e021abe2debb5456c9f02aa7300dd2b9d..a3fe7ef2d83b55b24c9deb3b48384b9a7c5c41bf 100644 (file)
--- 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;
 }