[PATCH 1/9] x86: Add a native_perf_sched_clock_from_tsc

Andi Kleen
2015-05-07T22:57:44Z

PEBSv3 has a raw TSC time stamp in its memory buffer that
later needs to to be converted to perf_clock. Add a
native_sched_clock_from_tsc() that works the same
as native_sched_clock, but starts with an already given TSC
value.

Right now I ignore paravirt for this. It will just get
the native clock. But there isn't para virtualized PEBS anyways.

Cc: tglx@linutronix.de
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
arch/x86/include/asm/tsc.h | 1 +
arch/x86/kernel/tsc.c | 8 ++++++++
2 files changed, 9 insertions(+)

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 94605c0..aad56eb 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -51,6 +51,7 @@ extern int unsynchronized_tsc(void);
extern int check_tsc_unstable(void);
extern int check_tsc_disabled(void);
extern unsigned long native_calibrate_tsc(void);
+extern unsigned long long native_sched_clock_from_tsc(u64 tsc);

extern int tsc_clocksource_reliable;

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 5054497..c16afd5 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -296,6 +296,14 @@ u64 native_sched_clock(void)
return cycles_2_ns(tsc_now);
}

+/*
+ * Generate a sched_clock if you already have a TSC value.
+ */
+u64 native_sched_clock_from_tsc(u64 tsc)
+{
+ return cycles_2_ns(tsc);
+}
+
/* We need to define a real function for sched_clock, to override the
weak default version */
#ifdef CONFIG_PARAVIRT
--
1.9.3