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Message-ID: <46102723.9050405@goop.org>
Date: Sun, 01 Apr 2007 14:41:55 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Andi Kleen <ak@...e.de>
CC: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] clean up tsc-based sched_clock
Three cleanups there:
- change "instable" -> "unstable"
- it's better to use get_cpu_var for getting this cpu's variables
- change cycles_2_ns to do the full computation rather than just the
tsc->ns scaling. It's a simpler interface, and it makes the function
more generally useful.
Signed-off-by: Jeremy Fitzhardinge <jeremy@...source.com>
---
arch/i386/kernel/sched-clock.c | 35 +++++++++++++++++++++--------------
1 file changed, 21 insertions(+), 14 deletions(-)
===================================================================
--- a/arch/i386/kernel/sched-clock.c
+++ b/arch/i386/kernel/sched-clock.c
@@ -39,17 +39,23 @@
struct sc_data {
unsigned int cyc2ns_scale;
- unsigned char instable;
+ unsigned char unstable;
unsigned long long last_tsc;
unsigned long long ns_base;
};
static DEFINE_PER_CPU(struct sc_data, sc_data);
-static inline unsigned long long cycles_2_ns(int cpu, unsigned long long cyc)
+static inline unsigned long long cycles_2_ns(unsigned long long cyc)
{
- struct sc_data *sc = &per_cpu(sc_data, cpu);
- return (cyc * sc->cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
+ const struct sc_data *sc = &__get_cpu_var(sc_data);
+ unsigned long long ns;
+
+ cyc -= sc->last_tsc;
+ ns = (cyc * sc->cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
+ ns += sc->ns_base;
+
+ return ns;
}
/*
@@ -62,18 +68,19 @@ static inline unsigned long long cycles_
*/
unsigned long long sched_clock(void)
{
- int cpu = get_cpu();
- struct sc_data *sc = &per_cpu(sc_data, cpu);
unsigned long long r;
+ const struct sc_data *sc = &get_cpu_var(sc_data);
- if (sc->instable) {
+ if (sc->unstable) {
/* TBD find a cheaper fallback timer than this */
r = ktime_to_ns(ktime_get());
} else {
get_scheduled_cycles(r);
- r = ((u64)sc->ns_base) + cycles_2_ns(cpu, r - sc->last_tsc);
+ r = cycles_2_ns(r);
}
- put_cpu();
+
+ put_cpu_var(sc_data);
+
return r;
}
@@ -81,7 +88,7 @@ static void resync_sc_freq(struct sc_dat
static void resync_sc_freq(struct sc_data *sc, unsigned int newfreq)
{
if (!cpu_has_tsc) {
- sc->instable = 1;
+ sc->unstable = 1;
return;
}
/* RED-PEN protect with seqlock? I hope that's not needed
@@ -90,7 +97,7 @@ static void resync_sc_freq(struct sc_dat
sc->ns_base = ktime_to_ns(ktime_get());
get_scheduled_cycles(sc->last_tsc);
sc->cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR) / newfreq;
- sc->instable = 0;
+ sc->unstable = 0;
}
static void call_r_s_f(void *arg)
@@ -119,9 +126,9 @@ static int sc_freq_event(struct notifier
switch (event) {
case CPUFREQ_RESUMECHANGE: /* needed? */
case CPUFREQ_PRECHANGE:
- /* Mark TSC as instable until cpu frequency change is done
+ /* Mark TSC as unstable until cpu frequency change is done
because we don't know when exactly it will change */
- sc->instable = 1;
+ sc->unstable = 1;
break;
case CPUFREQ_SUSPENDCHANGE:
case CPUFREQ_POSTCHANGE:
@@ -163,7 +170,7 @@ static __init int init_sched_clock(void)
int i;
struct cpufreq_freqs f = { .cpu = get_cpu(), .new = 0 };
for_each_possible_cpu (i)
- per_cpu(sc_data, i).instable = 1;
+ per_cpu(sc_data, i).unstable = 1;
WARN_ON(num_online_cpus() > 1);
call_r_s_f(&f);
put_cpu();
-
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