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hrtimers: Reorder clock bases

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The ordering of the clock bases is historical due to the
CLOCK_REALTIME and CLOCK_MONOTONIC constants. Now the hrtimer bases
have their own enumeration due to the gap between CLOCK_MONOTONIC and
CLOCK_BOOTTIME. So we can be more clever as most timers end up on the
CLOCK_MONOTONIC base due to the virtue of POSIX declaring that
relative CLOCK_REALTIME timers are not affected by time changes. In
desktop environments this is slowly changing as applications switch to
absolute timers, but I've observed empty CLOCK_REALTIME bases often
enough. There is no performance penalty or overhead when
CLOCK_REALTIME timers are active, but in case they are not we don't
skip over a full cache line.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
This commit is contained in:
Thomas Gleixner 2011-05-20 23:14:04 +02:00
parent ab8177bc53
commit 68fa61c026
2 changed files with 7 additions and 7 deletions
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2
include/linux/hrtimer.h
View file

@ -153,8 +153,8 @@ struct hrtimer_clock_base {
}; };
enum hrtimer_base_type { enum hrtimer_base_type {
HRTIMER_BASE_REALTIME,
HRTIMER_BASE_MONOTONIC, HRTIMER_BASE_MONOTONIC,
HRTIMER_BASE_REALTIME,
HRTIMER_BASE_BOOTTIME, HRTIMER_BASE_BOOTTIME,
HRTIMER_MAX_CLOCK_BASES, HRTIMER_MAX_CLOCK_BASES,
}; };

12
kernel/hrtimer.c
View file

@ -63,18 +63,18 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
.clock_base = .clock_base =
{ {
{
.index = HRTIMER_BASE_REALTIME,
.clockid = CLOCK_REALTIME,
.get_time = &ktime_get_real,
.resolution = KTIME_LOW_RES,
},
{ {
.index = HRTIMER_BASE_MONOTONIC, .index = HRTIMER_BASE_MONOTONIC,
.clockid = CLOCK_MONOTONIC, .clockid = CLOCK_MONOTONIC,
.get_time = &ktime_get, .get_time = &ktime_get,
.resolution = KTIME_LOW_RES, .resolution = KTIME_LOW_RES,
}, },
{
.index = HRTIMER_BASE_REALTIME,
.clockid = CLOCK_REALTIME,
.get_time = &ktime_get_real,
.resolution = KTIME_LOW_RES,
},
{ {
.index = HRTIMER_BASE_BOOTTIME, .index = HRTIMER_BASE_BOOTTIME,
.clockid = CLOCK_BOOTTIME, .clockid = CLOCK_BOOTTIME,