Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / kernel / trace / trace_clock.c

diff --git a/kernel/kernel/trace/trace_clock.c b/kernel/kernel/trace/trace_clock.c
new file mode 100644 (file)
index 0000000..57b67b1
--- /dev/null
+++ b/kernel/kernel/trace/trace_clock.c
@@ -0,0 +1,137 @@
+/*
+ * 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/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;
+}
+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();
+}
+
+/*
+ * 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);
+}
+
+/*
+ * 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;
+}
+
+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);
+}