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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2009-07-07 11:27:28 +0200
committerThomas Gleixner <tglx@linutronix.de>2009-07-07 12:47:33 +0200
commit951ed4d36b77ba9fe1ea08fc3c59d8bb6c9bda32 (patch)
tree870456aff2c513c00608f5416d1b7b440fa5f963 /kernel/hrtimer.c
parentfaf80d62e44dc627efb741f48db50c1858d1667c (diff)
downloadlinux-951ed4d36b77ba9fe1ea08fc3c59d8bb6c9bda32.tar.bz2
timekeeping: optimized ktime_get[_ts] for GENERIC_TIME=y
The generic ktime_get function defined in kernel/hrtimer.c is suboptimial for GENERIC_TIME=y: 0) | ktime_get() { 0) | ktime_get_ts() { 0) | getnstimeofday() { 0) | read_tod_clock() { 0) 0.601 us | } 0) 1.938 us | } 0) | set_normalized_timespec() { 0) 0.602 us | } 0) 4.375 us | } 0) 5.523 us | } Overall there are two read_seqbegin/read_seqretry loops and a lot of unnecessary struct timespec calculations. ktime_get returns a nano second value which is the sum of xtime, wall_to_monotonic and the nano second delta from the clock source. ktime_get can be optimized for GENERIC_TIME=y. The new version only calls clocksource_read: 0) | ktime_get() { 0) | read_tod_clock() { 0) 0.610 us | } 0) 1.977 us | } It uses a single read_seqbegin/readseqretry loop and just adds everthing to a nano second value. ktime_get_ts is optimized in a similar fashion. [ tglx: added WARN_ON(timekeeping_suspended) as in getnstimeofday() ] Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Acked-by: john stultz <johnstul@us.ibm.com> LKML-Reference: <20090707112728.3005244d@skybase> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/hrtimer.c')
-rw-r--r--kernel/hrtimer.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 9002958a96e7..829e0664b72e 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -48,6 +48,7 @@
#include <asm/uaccess.h>
+#ifndef CONFIG_GENERIC_TIME
/**
* ktime_get - get the monotonic time in ktime_t format
*
@@ -62,6 +63,7 @@ ktime_t ktime_get(void)
return timespec_to_ktime(now);
}
EXPORT_SYMBOL_GPL(ktime_get);
+#endif
/**
* ktime_get_real - get the real (wall-) time in ktime_t format
@@ -106,6 +108,7 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
}
};
+#ifndef CONFIG_GENERIC_TIME
/**
* ktime_get_ts - get the monotonic clock in timespec format
* @ts: pointer to timespec variable
@@ -130,6 +133,7 @@ void ktime_get_ts(struct timespec *ts)
ts->tv_nsec + tomono.tv_nsec);
}
EXPORT_SYMBOL_GPL(ktime_get_ts);
+#endif
/*
* Get the coarse grained time at the softirq based on xtime and