@@ -26,6 +26,7 @@ config X86
select HAVE_AOUT if X86_32
select HAVE_UNSTABLE_SCHED_CLOCK
select ARCH_SUPPORTS_NUMA_BALANCING
+ select ARCH_SUPPORTS_INT128 if X86_64
select ARCH_WANTS_PROT_NUMA_PROT_NONE
select HAVE_IDE
select HAVE_OPROFILE
@@ -4,6 +4,7 @@
#include <linux/pm.h>
#include <linux/percpu.h>
#include <linux/interrupt.h>
+#include <linux/math64.h>
#define TICK_SIZE (tick_nsec / 1000)
@@ -12,68 +13,5 @@ extern int recalibrate_cpu_khz(void);
extern int no_timer_check;
-/* Accelerators for sched_clock()
- * convert from cycles(64bits) => nanoseconds (64bits)
- * basic equation:
- * ns = cycles / (freq / ns_per_sec)
- * ns = cycles * (ns_per_sec / freq)
- * ns = cycles * (10^9 / (cpu_khz * 10^3))
- * ns = cycles * (10^6 / cpu_khz)
- *
- * Then we use scaling math (suggested by george@mvista.com) to get:
- * ns = cycles * (10^6 * SC / cpu_khz) / SC
- * ns = cycles * cyc2ns_scale / SC
- *
- * 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 precision, since
- * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
- * (mathieu.desnoyers@polymtl.ca)
- *
- * -johnstul@us.ibm.com "math is hard, lets go shopping!"
- *
- * In:
- *
- * ns = cycles * cyc2ns_scale / SC
- *
- * Although we may still have enough bits to store the value of ns,
- * in some cases, we may not have enough bits to store cycles * cyc2ns_scale,
- * leading to an incorrect result.
- *
- * To avoid this, we can decompose 'cycles' into quotient and remainder
- * of division by SC. Then,
- *
- * ns = (quot * SC + rem) * cyc2ns_scale / SC
- * = quot * cyc2ns_scale + (rem * cyc2ns_scale) / SC
- *
- * - sqazi@google.com
- */
-
-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)
-{
- int cpu = smp_processor_id();
- unsigned long long ns = per_cpu(cyc2ns_offset, cpu);
- ns += mult_frac(cyc, per_cpu(cyc2ns, cpu),
- (1UL << CYC2NS_SCALE_FACTOR));
- return ns;
-}
-
-static inline unsigned long long cycles_2_ns(unsigned long long cyc)
-{
- unsigned long long ns;
- unsigned long flags;
-
- local_irq_save(flags);
- ns = __cycles_2_ns(cyc);
- local_irq_restore(flags);
-
- return ns;
-}
#endif /* _ASM_X86_TIMER_H */
@@ -487,7 +487,7 @@ static void early_init_amd(struct cpuinfo_x86 *c)
set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
if (!check_tsc_unstable())
- sched_clock_stable = 1;
+ set_sched_clock_stable();
}
#ifdef CONFIG_X86_64
@@ -93,7 +93,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
if (!check_tsc_unstable())
- sched_clock_stable = 1;
+ set_sched_clock_stable();
}
/* Penwell and Cloverview have the TSC which doesn't sleep on S3 */
@@ -1895,7 +1895,8 @@ void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
userpg->cap_user_rdpmc = x86_pmu.attr_rdpmc;
userpg->pmc_width = x86_pmu.cntval_bits;
- if (!sched_clock_stable)
+#if 0
+ if (!sched_clock_stable())
return;
userpg->cap_user_time = 1;
@@ -1905,6 +1906,7 @@ void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
userpg->cap_user_time_zero = 1;
userpg->time_zero = this_cpu_read(cyc2ns_offset);
+#endif
}
/*
@@ -11,6 +11,7 @@
#include <linux/clocksource.h>
#include <linux/percpu.h>
#include <linux/timex.h>
+#include <linux/static_key.h>
#include <asm/hpet.h>
#include <asm/timer.h>
@@ -37,7 +38,95 @@ static int __read_mostly tsc_unstable;
erroneous rdtsc usage on !cpu_has_tsc processors */
static int __read_mostly tsc_disabled = -1;
+static struct static_key __use_tsc = STATIC_KEY_INIT;
+
int tsc_clocksource_reliable;
+
+/* Accelerators for sched_clock()
+ * convert from cycles(64bits) => nanoseconds (64bits)
+ * basic equation:
+ * ns = cycles / (freq / ns_per_sec)
+ * ns = cycles * (ns_per_sec / freq)
+ * ns = cycles * (10^9 / (cpu_khz * 10^3))
+ * ns = cycles * (10^6 / cpu_khz)
+ *
+ * Then we use scaling math (suggested by george@mvista.com) to get:
+ * ns = cycles * (10^6 * SC / cpu_khz) / SC
+ * ns = cycles * cyc2ns_scale / SC
+ *
+ * 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 precision, since
+ * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
+ * (mathieu.desnoyers@polymtl.ca)
+ *
+ * -johnstul@us.ibm.com "math is hard, lets go shopping!"
+ */
+
+struct cyc2ns_data {
+ unsigned long cyc2ns_mul;
+ unsigned long long cyc2ns_offset;
+};
+
+struct cyc2ns_latch {
+ unsigned int head, tail;
+ struct cyc2ns_data data[2];
+};
+
+static DEFINE_PER_CPU(struct cyc2ns_latch, cyc2ns);
+
+#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
+
+static inline unsigned long long cycles_2_ns(unsigned long long cyc)
+{
+ unsigned long long ns;
+ unsigned int tail, idx;
+
+again:
+ tail = this_cpu_read(cyc2ns.tail);
+ smp_rmb();
+ idx = tail & 1;
+ ns = this_cpu_read(cyc2ns.data[idx].cyc2ns_offset);
+ ns += mul_u64_u32_shr(cyc, this_cpu_read(cyc2ns.data[idx].cyc2ns_mul),
+ CYC2NS_SCALE_FACTOR);
+ smp_rmb();
+ if (unlikely(this_cpu_read(cyc2ns.head) - tail >= 2))
+ goto again;
+
+ return ns;
+}
+
+static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
+{
+ unsigned long long tsc_now, ns_now;
+ struct cyc2ns_latch *latch = &per_cpu(cyc2ns, cpu);
+ struct cyc2ns_data *data;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ sched_clock_idle_sleep_event();
+
+ if (!cpu_khz)
+ goto done;
+
+ latch->head++;
+ smp_wmb();
+ data = latch->data + (latch->head & 1);
+
+ rdtscll(tsc_now);
+ ns_now = cycles_2_ns(tsc_now);
+
+ data->cyc2ns_mul = ((NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR) + cpu_khz / 2) / cpu_khz;
+ data->cyc2ns_offset = ns_now - mul_u64_u32_shr(tsc_now, data->cyc2ns_mul, CYC2NS_SCALE_FACTOR);
+
+ smp_wmb();
+ latch->tail++;
+
+done:
+ sched_clock_idle_wakeup_event(0);
+ local_irq_restore(flags);
+}
/*
* Scheduler clock - returns current time in nanosec units.
*/
@@ -53,7 +142,7 @@ u64 native_sched_clock(void)
* very important for it to be as fast as the platform
* can achieve it. )
*/
- if (unlikely(tsc_disabled)) {
+ if (static_key_false(&__use_tsc)) {
/* No locking but a rare wrong value is not a big deal: */
return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
}
@@ -62,7 +151,7 @@ u64 native_sched_clock(void)
rdtscll(this_offset);
/* return the value in ns */
- return __cycles_2_ns(this_offset);
+ return cycles_2_ns(this_offset);
}
/* We need to define a real function for sched_clock, to override the
@@ -589,61 +678,11 @@ int recalibrate_cpu_khz(void)
EXPORT_SYMBOL(recalibrate_cpu_khz);
-/* Accelerators for sched_clock()
- * convert from cycles(64bits) => nanoseconds (64bits)
- * basic equation:
- * ns = cycles / (freq / ns_per_sec)
- * ns = cycles * (ns_per_sec / freq)
- * ns = cycles * (10^9 / (cpu_khz * 10^3))
- * ns = cycles * (10^6 / cpu_khz)
- *
- * Then we use scaling math (suggested by george@mvista.com) to get:
- * ns = cycles * (10^6 * SC / cpu_khz) / SC
- * ns = cycles * cyc2ns_scale / SC
- *
- * 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 precision, since
- * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
- * (mathieu.desnoyers@polymtl.ca)
- *
- * -johnstul@us.ibm.com "math is hard, lets go shopping!"
- */
-
-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, *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) {
- *scale = ((NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR) +
- cpu_khz / 2) / cpu_khz;
- *offset = ns_now - mult_frac(tsc_now, *scale,
- (1UL << CYC2NS_SCALE_FACTOR));
- }
-
- sched_clock_idle_wakeup_event(0);
- local_irq_restore(flags);
-}
-
static unsigned long long cyc2ns_suspend;
void tsc_save_sched_clock_state(void)
{
- if (!sched_clock_stable)
+ if (!sched_clock_stable())
return;
cyc2ns_suspend = sched_clock();
@@ -659,11 +698,12 @@ void tsc_save_sched_clock_state(void)
*/
void tsc_restore_sched_clock_state(void)
{
+#if 0
unsigned long long offset;
unsigned long flags;
int cpu;
- if (!sched_clock_stable)
+ if (!sched_clock_stable())
return;
local_irq_save(flags);
@@ -675,6 +715,7 @@ void tsc_restore_sched_clock_state(void)
per_cpu(cyc2ns_offset, cpu) = offset;
local_irq_restore(flags);
+#endif
}
#ifdef CONFIG_CPU_FREQ
@@ -795,7 +836,7 @@ void mark_tsc_unstable(char *reason)
{
if (!tsc_unstable) {
tsc_unstable = 1;
- sched_clock_stable = 0;
+ clear_sched_clock_stable();
disable_sched_clock_irqtime();
pr_info("Marking TSC unstable due to %s\n", reason);
/* Change only the rating, when not registered */
@@ -1002,7 +1043,9 @@ void __init tsc_init(void)
return;
/* now allow native_sched_clock() to use rdtsc */
+
tsc_disabled = 0;
+ static_key_slow_inc(&__use_tsc);
if (!no_sched_irq_time)
enable_sched_clock_irqtime();
@@ -133,4 +133,34 @@ __iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
return ret;
}
+#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
+
+#ifndef mul_u64_u32_shr
+static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
+{
+ return (u64)(((unsigned __int128)a * mul) >> shift);
+}
+#endif /* mul_u64_u32_shr */
+
+#else
+
+#ifndef mul_u64_u32_shr
+static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
+{
+ u32 ah, al;
+ u64 ret;
+
+ al = a;
+ ah = a >> 32;
+
+ ret = ((u64)al * mul) >> shift;
+ if (ah)
+ ret += ((u64)ah * mul) << (32 - shift);
+
+ return ret;
+}
+#endif /* mul_u64_u32_shr */
+
+#endif
+
#endif /* _LINUX_MATH64_H */
@@ -1880,7 +1880,9 @@ static inline void sched_clock_idle_wakeup_event(u64 delta_ns)
* but then during bootup it turns out that sched_clock()
* is reliable after all:
*/
-extern int sched_clock_stable;
+extern int sched_clock_stable(void);
+extern void set_sched_clock_stable(void);
+extern void clear_sched_clock_stable(void);
extern void sched_clock_tick(void);
extern void sched_clock_idle_sleep_event(void);
@@ -809,6 +809,12 @@ config GENERIC_SCHED_CLOCK
config ARCH_SUPPORTS_NUMA_BALANCING
bool
+#
+# For architectures that know their GCC __int128 support is sound
+#
+config ARCH_SUPPORTS_INT128
+ bool
+
# For architectures that (ab)use NUMA to represent different memory regions
# all cpu-local but of different latencies, such as SuperH.
#
@@ -26,9 +26,10 @@
* at 0 on boot (but people really shouldn't rely on that).
*
* cpu_clock(i) -- can be used from any context, including NMI.
- * sched_clock_cpu(i) -- must be used with local IRQs disabled (implied by NMI)
* local_clock() -- is cpu_clock() on the current cpu.
*
+ * sched_clock_cpu(i)
+ *
* How:
*
* The implementation either uses sched_clock() when
@@ -50,15 +51,6 @@
* Furthermore, explicit sleep and wakeup hooks allow us to account for time
* that is otherwise invisible (TSC gets stopped).
*
- *
- * Notes:
- *
- * The !IRQ-safetly of sched_clock() and sched_clock_cpu() comes from things
- * like cpufreq interrupts that can change the base clock (TSC) multiplier
- * and cause funny jumps in time -- although the filtering provided by
- * sched_clock_cpu() should mitigate serious artifacts we cannot rely on it
- * in general since for !CONFIG_HAVE_UNSTABLE_SCHED_CLOCK we fully rely on
- * sched_clock().
*/
#include <linux/spinlock.h>
#include <linux/hardirq.h>
@@ -66,6 +58,7 @@
#include <linux/percpu.h>
#include <linux/ktime.h>
#include <linux/sched.h>
+#include <linux/static_key.h>
/*
* Scheduler clock - returns current time in nanosec units.
@@ -82,7 +75,27 @@ EXPORT_SYMBOL_GPL(sched_clock);
__read_mostly int sched_clock_running;
#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
-__read_mostly int sched_clock_stable;
+static struct static_key __sched_clock_stable = STATIC_KEY_INIT;
+
+int sched_clock_stable(void)
+{
+ if (static_key_false(&__sched_clock_stable))
+ return false;
+ return true;
+}
+
+void set_sched_clock_stable(void)
+{
+ if (!sched_clock_stable())
+ static_key_slow_inc(&__sched_clock_stable);
+}
+
+void clear_sched_clock_stable(void)
+{
+ /* XXX worry about clock continuity */
+ if (sched_clock_stable())
+ static_key_slow_dec(&__sched_clock_stable);
+}
struct sched_clock_data {
u64 tick_raw;
@@ -244,7 +257,7 @@ u64 sched_clock_cpu(int cpu)
WARN_ON_ONCE(!irqs_disabled());
- if (sched_clock_stable)
+ if (sched_clock_stable())
return sched_clock();
if (unlikely(!sched_clock_running))
@@ -265,7 +278,7 @@ void sched_clock_tick(void)
struct sched_clock_data *scd;
u64 now, now_gtod;
- if (sched_clock_stable)
+ if (sched_clock_stable())
return;
if (unlikely(!sched_clock_running))
@@ -316,14 +329,10 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
*/
u64 cpu_clock(int cpu)
{
- u64 clock;
- unsigned long flags;
-
- local_irq_save(flags);
- clock = sched_clock_cpu(cpu);
- local_irq_restore(flags);
+ if (static_key_false(&__sched_clock_stable))
+ return sched_clock_cpu(cpu);
- return clock;
+ return sched_clock();
}
/*
@@ -335,14 +344,10 @@ u64 cpu_clock(int cpu)
*/
u64 local_clock(void)
{
- u64 clock;
- unsigned long flags;
+ if (static_key_false(&__sched_clock_stable))
+ return sched_clock_cpu(smp_processor_id());
- local_irq_save(flags);
- clock = sched_clock_cpu(smp_processor_id());
- local_irq_restore(flags);
-
- return clock;
+ return sched_clock();
}
#else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
@@ -362,12 +367,12 @@ u64 sched_clock_cpu(int cpu)
u64 cpu_clock(int cpu)
{
- return sched_clock_cpu(cpu);
+ return sched_clock();
}
u64 local_clock(void)
{
- return sched_clock_cpu(0);
+ return sched_clock();
}
#endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
@@ -371,7 +371,7 @@ static void sched_debug_header(struct seq_file *m)
PN(cpu_clk);
P(jiffies);
#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
- P(sched_clock_stable);
+ P(sched_clock_stable());
#endif
#undef PN
#undef P
@@ -177,7 +177,7 @@ static bool can_stop_full_tick(void)
* TODO: kick full dynticks CPUs when
* sched_clock_stable is set.
*/
- if (!sched_clock_stable) {
+ if (!sched_clock_stable()) {
trace_tick_stop(0, "unstable sched clock\n");
/*
* Don't allow the user to think they can get
@@ -2558,7 +2558,7 @@ rb_reserve_next_event(struct ring_buffer *buffer,
if (unlikely(test_time_stamp(delta))) {
int local_clock_stable = 1;
#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
- local_clock_stable = sched_clock_stable;
+ local_clock_stable = sched_clock_stable();
#endif
WARN_ONCE(delta > (1ULL << 59),
KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",