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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2009-07-07 11:27:28 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2009-07-07 12:47:33 +0200 |
| commit | 951ed4d36b77ba9fe1ea08fc3c59d8bb6c9bda32 (patch) | |
| tree | 870456aff2c513c00608f5416d1b7b440fa5f963 /kernel/hrtimer.c | |
| parent | faf80d62e44dc627efb741f48db50c1858d1667c (diff) | |
| download | lwn-951ed4d36b77ba9fe1ea08fc3c59d8bb6c9bda32.tar.gz lwn-951ed4d36b77ba9fe1ea08fc3c59d8bb6c9bda32.zip | |
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.c | 4 |
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 |