sched/clock, x86: Move some cyc2ns() code around
There are no __cycles_2_ns() users outside of arch/x86/kernel/tsc.c, so move it there. There are no cycles_2_ns() users. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-01lslnavfgo3kmbo4532zlcj@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra
Ingo Molnar
parent
5dd12c2152
commit
57c67da274
2 changed files with 61 additions and 110 deletions
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@ -13,66 +13,7 @@ extern int recalibrate_cpu_khz(void);
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extern int no_timer_check;
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/* Accelerators for sched_clock()
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* convert from cycles(64bits) => nanoseconds (64bits)
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* basic equation:
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* ns = cycles / (freq / ns_per_sec)
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* ns = cycles * (ns_per_sec / freq)
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* ns = cycles * (10^9 / (cpu_khz * 10^3))
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* ns = cycles * (10^6 / cpu_khz)
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*
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* Then we use scaling math (suggested by george@mvista.com) to get:
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* ns = cycles * (10^6 * SC / cpu_khz) / SC
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* ns = cycles * cyc2ns_scale / SC
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*
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* And since SC is a constant power of two, we can convert the div
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* into a shift.
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*
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* We can use khz divisor instead of mhz to keep a better precision, since
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* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
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* (mathieu.desnoyers@polymtl.ca)
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*
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* -johnstul@us.ibm.com "math is hard, lets go shopping!"
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*
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* In:
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*
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* ns = cycles * cyc2ns_scale / SC
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*
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* Although we may still have enough bits to store the value of ns,
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* in some cases, we may not have enough bits to store cycles * cyc2ns_scale,
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* leading to an incorrect result.
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*
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* To avoid this, we can decompose 'cycles' into quotient and remainder
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* of division by SC. Then,
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*
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* ns = (quot * SC + rem) * cyc2ns_scale / SC
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* = quot * cyc2ns_scale + (rem * cyc2ns_scale) / SC
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*
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* - sqazi@google.com
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*/
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DECLARE_PER_CPU(unsigned long, cyc2ns);
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DECLARE_PER_CPU(unsigned long long, cyc2ns_offset);
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#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
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static inline unsigned long long __cycles_2_ns(unsigned long long cyc)
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{
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unsigned long long ns = this_cpu_read(cyc2ns_offset);
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ns += mul_u64_u32_shr(cyc, this_cpu_read(cyc2ns), CYC2NS_SCALE_FACTOR);
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return ns;
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}
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static inline unsigned long long cycles_2_ns(unsigned long long cyc)
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{
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unsigned long long ns;
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unsigned long flags;
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local_irq_save(flags);
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ns = __cycles_2_ns(cyc);
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local_irq_restore(flags);
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return ns;
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}
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#endif /* _ASM_X86_TIMER_H */
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@ -38,6 +38,66 @@ static int __read_mostly tsc_unstable;
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static int __read_mostly tsc_disabled = -1;
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int tsc_clocksource_reliable;
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/* Accelerators for sched_clock()
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* convert from cycles(64bits) => nanoseconds (64bits)
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* basic equation:
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* ns = cycles / (freq / ns_per_sec)
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* ns = cycles * (ns_per_sec / freq)
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* ns = cycles * (10^9 / (cpu_khz * 10^3))
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* ns = cycles * (10^6 / cpu_khz)
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*
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* Then we use scaling math (suggested by george@mvista.com) to get:
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* ns = cycles * (10^6 * SC / cpu_khz) / SC
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* ns = cycles * cyc2ns_scale / SC
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*
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* And since SC is a constant power of two, we can convert the div
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* into a shift.
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*
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* We can use khz divisor instead of mhz to keep a better precision, since
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* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
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* (mathieu.desnoyers@polymtl.ca)
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*
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* -johnstul@us.ibm.com "math is hard, lets go shopping!"
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*/
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DEFINE_PER_CPU(unsigned long, cyc2ns);
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DEFINE_PER_CPU(unsigned long long, cyc2ns_offset);
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#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
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static inline unsigned long long cycles_2_ns(unsigned long long cyc)
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{
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unsigned long long ns = this_cpu_read(cyc2ns_offset);
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ns += mul_u64_u32_shr(cyc, this_cpu_read(cyc2ns), CYC2NS_SCALE_FACTOR);
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return ns;
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}
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static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
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{
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unsigned long long tsc_now, ns_now, *offset;
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unsigned long flags, *scale;
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local_irq_save(flags);
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sched_clock_idle_sleep_event();
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scale = &per_cpu(cyc2ns, cpu);
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offset = &per_cpu(cyc2ns_offset, cpu);
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rdtscll(tsc_now);
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ns_now = cycles_2_ns(tsc_now);
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if (cpu_khz) {
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*scale = ((NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR) +
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cpu_khz / 2) / cpu_khz;
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*offset = ns_now - mult_frac(tsc_now, *scale,
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(1UL << CYC2NS_SCALE_FACTOR));
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}
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sched_clock_idle_wakeup_event(0);
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local_irq_restore(flags);
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}
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/*
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* Scheduler clock - returns current time in nanosec units.
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*/
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@ -62,7 +122,7 @@ u64 native_sched_clock(void)
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rdtscll(this_offset);
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/* return the value in ns */
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return __cycles_2_ns(this_offset);
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return cycles_2_ns(this_offset);
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}
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/* We need to define a real function for sched_clock, to override the
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@ -589,56 +649,6 @@ int recalibrate_cpu_khz(void)
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EXPORT_SYMBOL(recalibrate_cpu_khz);
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/* Accelerators for sched_clock()
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* convert from cycles(64bits) => nanoseconds (64bits)
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* basic equation:
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* ns = cycles / (freq / ns_per_sec)
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* ns = cycles * (ns_per_sec / freq)
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* ns = cycles * (10^9 / (cpu_khz * 10^3))
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* ns = cycles * (10^6 / cpu_khz)
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*
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* Then we use scaling math (suggested by george@mvista.com) to get:
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* ns = cycles * (10^6 * SC / cpu_khz) / SC
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* ns = cycles * cyc2ns_scale / SC
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*
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* And since SC is a constant power of two, we can convert the div
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* into a shift.
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*
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* We can use khz divisor instead of mhz to keep a better precision, since
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* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
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* (mathieu.desnoyers@polymtl.ca)
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*
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* -johnstul@us.ibm.com "math is hard, lets go shopping!"
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*/
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DEFINE_PER_CPU(unsigned long, cyc2ns);
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DEFINE_PER_CPU(unsigned long long, cyc2ns_offset);
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static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
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{
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unsigned long long tsc_now, ns_now, *offset;
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unsigned long flags, *scale;
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local_irq_save(flags);
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sched_clock_idle_sleep_event();
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scale = &per_cpu(cyc2ns, cpu);
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offset = &per_cpu(cyc2ns_offset, cpu);
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rdtscll(tsc_now);
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ns_now = __cycles_2_ns(tsc_now);
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if (cpu_khz) {
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*scale = ((NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR) +
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cpu_khz / 2) / cpu_khz;
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*offset = ns_now - mult_frac(tsc_now, *scale,
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(1UL << CYC2NS_SCALE_FACTOR));
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}
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sched_clock_idle_wakeup_event(0);
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local_irq_restore(flags);
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}
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static unsigned long long cyc2ns_suspend;
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void tsc_save_sched_clock_state(void)
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