tracing: implement trace_clock_*() APIs

Impact: implement new tracing timestamp APIs

Add three 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

Make the ring-buffer use the local trace clock internally.

Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 3 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 8f19f1aa42b0..a8c275c01e83 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -4,6 +4,7 @@
  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
  */
 #include <linux/ring_buffer.h>
+#include <linux/trace_clock.h>
 #include <linux/ftrace_irq.h>
 #include <linux/spinlock.h>
 #include <linux/debugfs.h>
@@ -12,7 +13,6 @@
 #include <linux/module.h>
 #include <linux/percpu.h>
 #include <linux/mutex.h>
-#include <linux/sched.h>        /* used for sched_clock() (for now) */
 #include <linux/init.h>
 #include <linux/hash.h>
 #include <linux/list.h>
@@ -112,14 +112,13 @@ EXPORT_SYMBOL_GPL(tracing_is_on);
 /* Up this if you want to test the TIME_EXTENTS and normalization */
 #define DEBUG_SHIFT 0
 
-/* FIXME!!! */
 u64 ring_buffer_time_stamp(int cpu)
 {
         u64 time;
 
         preempt_disable_notrace();
         /* shift to debug/test normalization and TIME_EXTENTS */
-        time = sched_clock() << DEBUG_SHIFT;
+        time = trace_clock_local() << DEBUG_SHIFT;
         preempt_enable_no_resched_notrace();
 
         return time;