Add a new powerpc-specific trace clock using the timebase register,
similar to x86-tsc. This gives us a fast, monotonic, cross-cpu clock
for trace entries and can be used to correlate events across cpus as
well as across hypervisor and guest (assuming it is not a migrated guest
with a non-zero tb_offset).
Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
---
I have followed the approach used by x86-tsc here, but we could get rid of
trace_clock.c if we directly use get_tb() with perhaps the notrace annotation.
Would that be preferable?
Thanks,
Naveen
Documentation/trace/ftrace.txt | 5 +++++
arch/powerpc/include/asm/Kbuild | 1 -
arch/powerpc/include/asm/trace_clock.h | 27 +++++++++++++++++++++++++++
arch/powerpc/kernel/Makefile | 1 +
arch/powerpc/kernel/trace_clock.c | 15 +++++++++++++++
5 files changed, 48 insertions(+), 1 deletion(-)
create mode 100644 arch/powerpc/include/asm/trace_clock.h
create mode 100644 arch/powerpc/kernel/trace_clock.c
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 572ca92..689f61a 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -346,6 +346,11 @@ of ftrace. Here is a list of some of the key files:
x86-tsc: Architectures may define their own clocks. For
example, x86 uses its own TSC cycle clock here.
+ ppc-tb: This uses the powerpc timebase register value.
+ This is in sync across CPUs and can also be used
+ to correlate events across hypervisor/guest if
+ tb_offset is known.
+
To set a clock, simply echo the clock name into this file.
echo global > trace_clock
diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild
index 382b28e..5041c66 100644
--- a/arch/powerpc/include/asm/Kbuild
+++ b/arch/powerpc/include/asm/Kbuild
@@ -5,5 +5,4 @@ generic-y += mcs_spinlock.h
generic-y += preempt.h
generic-y += rwsem.h
generic-y += scatterlist.h
-generic-y += trace_clock.h
generic-y += vtime.h
diff --git a/arch/powerpc/include/asm/trace_clock.h
b/arch/powerpc/include/asm/trace_clock.h
new file mode 100644
index 0000000..0b0d094
--- /dev/null
+++ b/arch/powerpc/include/asm/trace_clock.h
@@ -0,0 +1,27 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * Copyright (C) 2015 Naveen N. Rao, IBM Corporation
+ */
+
+#ifndef _ASM_PPC_TRACE_CLOCK_H
+#define _ASM_PPC_TRACE_CLOCK_H
+
+#include <linux/compiler.h>
+#include <linux/types.h>
+
+#ifdef CONFIG_TRACE_CLOCK
+
+extern u64 notrace trace_clock_ppc_tb(void);
+
+#define ARCH_TRACE_CLOCKS { trace_clock_ppc_tb, "ppc-tb", 0 },
+
+#else
+
+#define ARCH_TRACE_CLOCKS
+
+#endif /* CONFIG_TRACE_CLOCK */
+
+#endif /* _ASM_PPC_TRACE_CLOCK_H */
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 502cf69..f9936f3 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -118,6 +118,7 @@ obj-$(CONFIG_PPC_IO_WORKAROUNDS) += io-workarounds.o
obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o
+obj-$(CONFIG_TRACE_CLOCK) += trace_clock.o
ifneq ($(CONFIG_PPC_INDIRECT_PIO),y)
obj-y += iomap.o
diff --git a/arch/powerpc/kernel/trace_clock.c
b/arch/powerpc/kernel/trace_clock.c
new file mode 100644
index 0000000..4917069
--- /dev/null
+++ b/arch/powerpc/kernel/trace_clock.c
@@ -0,0 +1,15 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * Copyright (C) 2015 Naveen N. Rao, IBM Corporation
+ */
+
+#include <asm/trace_clock.h>
+#include <asm/time.h>
+
+u64 notrace trace_clock_ppc_tb(void)
+{
+ return get_tb();
+}
--
2.3.5
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