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, 19 insertions, 0 deletions

diff --git a/include/linux/trace_clock.h b/include/linux/trace_clock.h
new file mode 100644
index 000000000000..7a8130384087
--- /dev/null
+++ b/include/linux/trace_clock.h
@@ -0,0 +1,19 @@
+#ifndef _LINUX_TRACE_CLOCK_H
+#define _LINUX_TRACE_CLOCK_H
+
+/*
+ * 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
+ */
+#include <linux/compiler.h>
+#include <linux/types.h>
+
+extern u64 notrace trace_clock_local(void);
+extern u64 notrace trace_clock(void);
+extern u64 notrace trace_clock_global(void);
+
+#endif /* _LINUX_TRACE_CLOCK_H */