x86: scale cyc_2_nsec according to CPU frequency
scale the sched_clock() cyc_2_nsec scaling factor according to
CPU frequency changes.
[ mingo@elte.hu: simplified it and fixed it for SMP. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index 9ebc0da..00bb4c1 100644
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -5,6 +5,7 @@
#include <linux/jiffies.h>
#include <linux/init.h>
#include <linux/dmi.h>
+#include <linux/percpu.h>
#include <asm/delay.h>
#include <asm/tsc.h>
@@ -80,13 +81,31 @@
*
* -johnstul@us.ibm.com "math is hard, lets go shopping!"
*/
-unsigned long cyc2ns_scale __read_mostly;
-#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
+DEFINE_PER_CPU(unsigned long, cyc2ns);
-static inline void set_cyc2ns_scale(unsigned long cpu_khz)
+static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
{
- cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
+ unsigned long flags, prev_scale, *scale;
+ unsigned long long tsc_now, ns_now;
+
+ local_irq_save(flags);
+ sched_clock_idle_sleep_event();
+
+ scale = &per_cpu(cyc2ns, cpu);
+
+ rdtscll(tsc_now);
+ ns_now = __cycles_2_ns(tsc_now);
+
+ prev_scale = *scale;
+ if (cpu_khz)
+ *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;
+
+ /*
+ * Start smoothly with the new frequency:
+ */
+ sched_clock_idle_wakeup_event(0);
+ local_irq_restore(flags);
}
/*
@@ -239,7 +258,9 @@
ref_freq, freq->new);
if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
tsc_khz = cpu_khz;
- set_cyc2ns_scale(cpu_khz);
+ preempt_disable();
+ set_cyc2ns_scale(cpu_khz, smp_processor_id());
+ preempt_enable();
/*
* TSC based sched_clock turns
* to junk w/ cpufreq
@@ -367,6 +388,8 @@
void __init tsc_init(void)
{
+ int cpu;
+
if (!cpu_has_tsc || tsc_disable)
goto out_no_tsc;
@@ -380,7 +403,15 @@
(unsigned long)cpu_khz / 1000,
(unsigned long)cpu_khz % 1000);
- set_cyc2ns_scale(cpu_khz);
+ /*
+ * Secondary CPUs do not run through tsc_init(), so set up
+ * all the scale factors for all CPUs, assuming the same
+ * speed as the bootup CPU. (cpufreq notifiers will fix this
+ * up if their speed diverges)
+ */
+ for_each_possible_cpu(cpu)
+ set_cyc2ns_scale(cpu_khz, cpu);
+
use_tsc_delay();
/* Check and install the TSC clocksource */