The patch titled
x86: fix cpufreq tsc scaling
has been removed from the -mm tree. Its filename was
x86-fix-cpufreq-tsc-scaling.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: x86: fix cpufreq tsc scaling
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
For freqency dependent TSCs we only scale the cycles, we do not account
for the discrepancy in absolute value. Add a constant factor so that:
c1 + f1*cyc == c2 + f2*cyc
LKML-Reference: <new-submission>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Chucked-on-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/timer.h | 6 +++++-
arch/x86/kernel/tsc.c | 8 ++++++--
2 files changed, 11 insertions(+), 3 deletions(-)
diff -puN arch/x86/include/asm/timer.h~x86-fix-cpufreq-tsc-scaling arch/x86/include/asm/timer.h
--- a/arch/x86/include/asm/timer.h~x86-fix-cpufreq-tsc-scaling
+++ a/arch/x86/include/asm/timer.h
@@ -45,12 +45,16 @@ extern int no_timer_check;
*/
DECLARE_PER_CPU(unsigned long, cyc2ns);
+DECLARE_PER_CPU(unsigned long long, cyc2ns_offset);
#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
static inline unsigned long long __cycles_2_ns(unsigned long long cyc)
{
- return cyc * per_cpu(cyc2ns, smp_processor_id()) >> CYC2NS_SCALE_FACTOR;
+ int cpu = smp_processor_id();
+ unsigned long long ns = per_cpu(cyc2ns_offset, cpu);
+ ns += cyc * per_cpu(cyc2ns, cpu) >> CYC2NS_SCALE_FACTOR;
+ return ns;
}
static inline unsigned long long cycles_2_ns(unsigned long long cyc)
diff -puN arch/x86/kernel/tsc.c~x86-fix-cpufreq-tsc-scaling arch/x86/kernel/tsc.c
--- a/arch/x86/kernel/tsc.c~x86-fix-cpufreq-tsc-scaling
+++ a/arch/x86/kernel/tsc.c
@@ -590,22 +590,26 @@ EXPORT_SYMBOL(recalibrate_cpu_khz);
*/
DEFINE_PER_CPU(unsigned long, cyc2ns);
+DEFINE_PER_CPU(unsigned long long, cyc2ns_offset);
static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
{
- unsigned long long tsc_now, ns_now;
+ unsigned long long tsc_now, ns_now, *offset;
unsigned long flags, *scale;
local_irq_save(flags);
sched_clock_idle_sleep_event();
scale = &per_cpu(cyc2ns, cpu);
+ offset = &per_cpu(cyc2ns_offset, cpu);
rdtscll(tsc_now);
ns_now = __cycles_2_ns(tsc_now);
- if (cpu_khz)
+ if (cpu_khz) {
*scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;
+ *offset = ns_now - (tsc_now * *scale >> CYC2NS_SCALE_FACTOR);
+ }
sched_clock_idle_wakeup_event(0);
local_irq_restore(flags);
_
Patches currently in -mm which might be from peterz@xxxxxxxxxxxxx are
origin.patch
linux-next.patch
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