Release 4.15 kernel/trace/trace_clock.c
/*
* tracing clocks
*
* Copyright (C) 2009 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
*
* Implements 3 trace clock variants, with differing scalability/precision
* tradeoffs:
*
* - local: CPU-local trace clock
* - medium: scalable global clock with some jitter
* - global: globally monotonic, serialized clock
*
* Tracer plugins will chose a default from these clocks.
*/
#include <linux/spinlock.h>
#include <linux/irqflags.h>
#include <linux/hardirq.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
#include <linux/ktime.h>
#include <linux/trace_clock.h>
/*
* trace_clock_local(): the simplest and least coherent tracing clock.
*
* Useful for tracing that does not cross to other CPUs nor
* does it go through idle events.
*/
u64 notrace trace_clock_local(void)
{
u64 clock;
/*
* sched_clock() is an architecture implemented, fast, scalable,
* lockless clock. It is not guaranteed to be coherent across
* CPUs, nor across CPU idle events.
*/
preempt_disable_notrace();
clock = sched_clock();
preempt_enable_notrace();
return clock;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 12 | 46.15% | 1 | 25.00% |
| Peter Zijlstra | 10 | 38.46% | 1 | 25.00% |
| Steven Rostedt | 4 | 15.38% | 2 | 50.00% |
| Total | 26 | 100.00% | 4 | 100.00% |
EXPORT_SYMBOL_GPL(trace_clock_local);
/*
* trace_clock(): 'between' trace clock. Not completely serialized,
* but not completely incorrect when crossing CPUs either.
*
* This is based on cpu_clock(), which will allow at most ~1 jiffy of
* jitter between CPUs. So it's a pretty scalable clock, but there
* can be offsets in the trace data.
*/
u64 notrace trace_clock(void)
{
return local_clock();
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 11 | 91.67% | 1 | 50.00% |
| Peter Zijlstra | 1 | 8.33% | 1 | 50.00% |
| Total | 12 | 100.00% | 2 | 100.00% |
EXPORT_SYMBOL_GPL(trace_clock);
/*
* trace_jiffy_clock(): Simply use jiffies as a clock counter.
* Note that this use of jiffies_64 is not completely safe on
* 32-bit systems. But the window is tiny, and the effect if
* we are affected is that we will have an obviously bogus
* timestamp on a trace event - i.e. not life threatening.
*/
u64 notrace trace_clock_jiffies(void)
{
return jiffies_64_to_clock_t(jiffies_64 - INITIAL_JIFFIES);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Steven Rostedt | 12 | 75.00% | 1 | 50.00% |
| Tony Luck | 4 | 25.00% | 1 | 50.00% |
| Total | 16 | 100.00% | 2 | 100.00% |
EXPORT_SYMBOL_GPL(trace_clock_jiffies);
/*
* trace_clock_global(): special globally coherent trace clock
*
* It has higher overhead than the other trace clocks but is still
* an order of magnitude faster than GTOD derived hardware clocks.
*
* Used by plugins that need globally coherent timestamps.
*/
/* keep prev_time and lock in the same cacheline. */
static struct {
u64 prev_time;
arch_spinlock_t lock;
} trace_clock_struct ____cacheline_aligned_in_smp =
{
.lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED,
};
u64 notrace trace_clock_global(void)
{
unsigned long flags;
int this_cpu;
u64 now;
local_irq_save(flags);
this_cpu = raw_smp_processor_id();
now = sched_clock_cpu(this_cpu);
/*
* If in an NMI context then dont risk lockups and return the
* cpu_clock() time:
*/
if (unlikely(in_nmi()))
goto out;
arch_spin_lock(&trace_clock_struct.lock);
/*
* TODO: if this happens often then maybe we should reset
* my_scd->clock to prev_time+1, to make sure
* we start ticking with the local clock from now on?
*/
if ((s64)(now - trace_clock_struct.prev_time) < 0)
now = trace_clock_struct.prev_time + 1;
trace_clock_struct.prev_time = now;
arch_spin_unlock(&trace_clock_struct.lock);
out:
local_irq_restore(flags);
return now;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 82 | 79.61% | 1 | 20.00% |
| Steven Rostedt | 16 | 15.53% | 1 | 20.00% |
| Thomas Gleixner | 2 | 1.94% | 1 | 20.00% |
| Li Zefan | 2 | 1.94% | 1 | 20.00% |
| Namhyung Kim | 1 | 0.97% | 1 | 20.00% |
| Total | 103 | 100.00% | 5 | 100.00% |
EXPORT_SYMBOL_GPL(trace_clock_global);
static atomic64_t trace_counter;
/*
* trace_clock_counter(): simply an atomic counter.
* Use the trace_counter "counter" for cases where you do not care
* about timings, but are interested in strict ordering.
*/
u64 notrace trace_clock_counter(void)
{
return atomic64_add_return(1, &trace_counter);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Steven Rostedt | 17 | 100.00% | 1 | 100.00% |
| Total | 17 | 100.00% | 1 | 100.00% |
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Ingo Molnar | 136 | 53.33% | 2 | 10.00% |
| Steven Rostedt | 68 | 26.67% | 5 | 25.00% |
| Jerry Snitselaar | 15 | 5.88% | 1 | 5.00% |
| Peter Zijlstra | 11 | 4.31% | 2 | 10.00% |
| Paul E. McKenney | 5 | 1.96% | 1 | 5.00% |
| Thomas Gleixner | 5 | 1.96% | 3 | 15.00% |
| Tony Luck | 5 | 1.96% | 1 | 5.00% |
| Dmitri Vorobiev | 3 | 1.18% | 1 | 5.00% |
| Frédéric Weisbecker | 3 | 1.18% | 1 | 5.00% |
| Li Zefan | 2 | 0.78% | 1 | 5.00% |
| Lucas De Marchi | 1 | 0.39% | 1 | 5.00% |
| Namhyung Kim | 1 | 0.39% | 1 | 5.00% |
| Total | 255 | 100.00% | 20 | 100.00% |
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