diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2013-11-28 19:38:42 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2014-01-13 15:13:13 +0100 |
| commit | 35af99e646c7f7ea46dc2977601e9e71a51dadd5 (patch) | |
| tree | d999820d233844278549cd826c4bfd6c7aa1ecc8 /kernel/sched | |
| parent | ef08f0fff87630d4f67ceb09514d8b444df833f8 (diff) | |
| download | linux-35af99e646c7f7ea46dc2977601e9e71a51dadd5.tar.bz2 | |
sched/clock, x86: Use a static_key for sched_clock_stable
In order to avoid the runtime condition and variable load turn
sched_clock_stable into a static_key.
Also provide a shorter implementation of local_clock() and
cpu_clock(int) when sched_clock_stable==1.
MAINLINE PRE POST
sched_clock_stable: 1 1 1
(cold) sched_clock: 329841 221876 215295
(cold) local_clock: 301773 234692 220773
(warm) sched_clock: 38375 25602 25659
(warm) local_clock: 100371 33265 27242
(warm) rdtsc: 27340 24214 24208
sched_clock_stable: 0 0 0
(cold) sched_clock: 382634 235941 237019
(cold) local_clock: 396890 297017 294819
(warm) sched_clock: 38194 25233 25609
(warm) local_clock: 143452 71234 71232
(warm) rdtsc: 27345 24245 24243
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-eummbdechzz37mwmpags1gjr@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/clock.c | 41 | ||||
| -rw-r--r-- | kernel/sched/debug.c | 2 |
2 files changed, 35 insertions, 8 deletions
diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index 59371549ddf0..c9b34c4e3ecc 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -58,6 +58,7 @@ #include <linux/percpu.h> #include <linux/ktime.h> #include <linux/sched.h> +#include <linux/static_key.h> /* * Scheduler clock - returns current time in nanosec units. @@ -74,7 +75,27 @@ EXPORT_SYMBOL_GPL(sched_clock); __read_mostly int sched_clock_running; #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK -__read_mostly int sched_clock_stable; +static struct static_key __sched_clock_stable = STATIC_KEY_INIT; + +int sched_clock_stable(void) +{ + if (static_key_false(&__sched_clock_stable)) + return false; + return true; +} + +void set_sched_clock_stable(void) +{ + if (!sched_clock_stable()) + static_key_slow_dec(&__sched_clock_stable); +} + +void clear_sched_clock_stable(void) +{ + /* XXX worry about clock continuity */ + if (sched_clock_stable()) + static_key_slow_inc(&__sched_clock_stable); +} struct sched_clock_data { u64 tick_raw; @@ -234,7 +255,7 @@ u64 sched_clock_cpu(int cpu) struct sched_clock_data *scd; u64 clock; - if (sched_clock_stable) + if (sched_clock_stable()) return sched_clock(); if (unlikely(!sched_clock_running)) @@ -257,7 +278,7 @@ void sched_clock_tick(void) struct sched_clock_data *scd; u64 now, now_gtod; - if (sched_clock_stable) + if (sched_clock_stable()) return; if (unlikely(!sched_clock_running)) @@ -308,7 +329,10 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event); */ u64 cpu_clock(int cpu) { - return sched_clock_cpu(cpu); + if (static_key_false(&__sched_clock_stable)) + return sched_clock_cpu(cpu); + + return sched_clock(); } /* @@ -320,7 +344,10 @@ u64 cpu_clock(int cpu) */ u64 local_clock(void) { - return sched_clock_cpu(raw_smp_processor_id()); + if (static_key_false(&__sched_clock_stable)) + return sched_clock_cpu(raw_smp_processor_id()); + + return sched_clock(); } #else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ @@ -340,12 +367,12 @@ u64 sched_clock_cpu(int cpu) u64 cpu_clock(int cpu) { - return sched_clock_cpu(cpu); + return sched_clock(); } u64 local_clock(void) { - return sched_clock_cpu(0); + return sched_clock(); } #endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 374fe04a5e6e..dd52e7ffb10e 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -371,7 +371,7 @@ static void sched_debug_header(struct seq_file *m) PN(cpu_clk); P(jiffies); #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK - P(sched_clock_stable); + P(sched_clock_stable()); #endif #undef PN #undef P |