"Guillaume Chazarain" <[EMAIL PROTECTED]> wrote:
> On Dec 7, 2007 6:51 AM, Thomas Gleixner <[EMAIL PROTECTED]> wrote:
> > Hmrpf. sched_clock() is used for the time stamp of the printks. We
> > need to find some better solution other than killing off the tsc
> > access completely.
>
> Something like http://lkml.org/lkml/2007/3/16/291 that would need some
> refresh?
And here is a refreshed one just for testing with 2.6-git. The 64 bit
part is a shamelessly untested copy/paste as I cannot test it.
diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index 9ebc0da..d561b2f 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>
@@ -78,15 +79,32 @@ EXPORT_SYMBOL_GPL(check_tsc_unstable);
* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
* ([EMAIL PROTECTED])
*
+ * ns += offset to avoid sched_clock jumps with cpufreq
+ *
* [EMAIL PROTECTED] "math is hard, lets go shopping!"
*/
-unsigned long cyc2ns_scale __read_mostly;
#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
-static inline void set_cyc2ns_scale(unsigned long cpu_khz)
+DEFINE_PER_CPU(struct cyc2ns_params, cyc2ns) __read_mostly;
+
+static void set_cyc2ns_scale(unsigned long cpu_khz)
{
- cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
+ struct cyc2ns_params *params;
+ unsigned long flags;
+ unsigned long long tsc_now, ns_now;
+
+ rdtscll(tsc_now);
+ params = &get_cpu_var(cyc2ns);
+
+ local_irq_save(flags);
+ ns_now = __cycles_2_ns(params, tsc_now);
+
+ params->scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;
+ params->offset += ns_now - __cycles_2_ns(params, tsc_now);
+ local_irq_restore(flags);
+
+ put_cpu_var(cyc2ns);
}
/*
diff --git a/arch/x86/kernel/tsc_64.c b/arch/x86/kernel/tsc_64.c
index 9c70af4..93e7a06 100644
--- a/arch/x86/kernel/tsc_64.c
+++ b/arch/x86/kernel/tsc_64.c
@@ -10,6 +10,7 @@
#include <asm/hpet.h>
#include <asm/timex.h>
+#include <asm/timer.h>
static int notsc __initdata = 0;
@@ -18,16 +19,25 @@ EXPORT_SYMBOL(cpu_khz);
unsigned int tsc_khz;
EXPORT_SYMBOL(tsc_khz);
-static unsigned int cyc2ns_scale __read_mostly;
+DEFINE_PER_CPU(struct cyc2ns_params, cyc2ns) __read_mostly;
-static inline void set_cyc2ns_scale(unsigned long khz)
+static void set_cyc2ns_scale(unsigned long cpu_khz)
{
- cyc2ns_scale = (NSEC_PER_MSEC << NS_SCALE) / khz;
-}
+ struct cyc2ns_params *params;
+ unsigned long flags;
+ unsigned long long tsc_now, ns_now;
-static unsigned long long cycles_2_ns(unsigned long long cyc)
-{
- return (cyc * cyc2ns_scale) >> NS_SCALE;
+ rdtscll(tsc_now);
+ params = &get_cpu_var(cyc2ns);
+
+ local_irq_save(flags);
+ ns_now = __cycles_2_ns(params, tsc_now);
+
+ params->scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;
+ params->offset += ns_now - __cycles_2_ns(params, tsc_now);
+ local_irq_restore(flags);
+
+ put_cpu_var(cyc2ns);
}
unsigned long long sched_clock(void)
diff --git a/include/asm-x86/timer.h b/include/asm-x86/timer.h
index 0db7e99..ff4f2a3 100644
--- a/include/asm-x86/timer.h
+++ b/include/asm-x86/timer.h
@@ -2,6 +2,7 @@
#define _ASMi386_TIMER_H
#include <linux/init.h>
#include <linux/pm.h>
+#include <linux/percpu.h>
#define TICK_SIZE (tick_nsec / 1000)
@@ -16,7 +17,7 @@ extern int recalibrate_cpu_khz(void);
#define calculate_cpu_khz() native_calculate_cpu_khz()
#endif
-/* Accellerators for sched_clock()
+/* Accelerators for sched_clock()
* convert from cycles(64bits) => nanoseconds (64bits)
* basic equation:
* ns = cycles / (freq / ns_per_sec)
@@ -31,20 +32,44 @@ extern int recalibrate_cpu_khz(void);
* And since SC is a constant power of two, we can convert the div
* into a shift.
*
- * We can use khz divisor instead of mhz to keep a better percision, since
+ * We can use khz divisor instead of mhz to keep a better precision, since
* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
* ([EMAIL PROTECTED])
*
+ * ns += offset to avoid sched_clock jumps with cpufreq
+ *
* [EMAIL PROTECTED] "math is hard, lets go shopping!"
*/
-extern unsigned long cyc2ns_scale __read_mostly;
+
+struct cyc2ns_params {
+ unsigned long scale;
+ unsigned long long offset;
+};
+
+DECLARE_PER_CPU(struct cyc2ns_params, cyc2ns) __read_mostly;
#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
-static inline unsigned long long cycles_2_ns(unsigned long long cyc)
+static inline unsigned long long __cycles_2_ns(struct cyc2ns_params *params,
+ unsigned long long cyc)
{
- return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
+ return ((cyc * params->scale) >> CYC2NS_SCALE_FACTOR) + params->offset;
}
+static inline unsigned long long cycles_2_ns(unsigned long long cyc)
+{
+ struct cyc2ns_params *params;
+ unsigned long flags;
+ unsigned long long ns;
+
+ params = &get_cpu_var(cyc2ns);
+
+ local_irq_save(flags);
+ ns = __cycles_2_ns(params, cyc);
+ local_irq_restore(flags);
+
+ put_cpu_var(cyc2ns);
+ return ns;
+}
#endif
--
Guillaume
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