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authorNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>2015-04-24 14:24:44 +0530
committerMichael Ellerman <mpe@ellerman.id.au>2015-08-06 16:36:23 +1000
commit197165d44925bd0fa892990851dee4d312a44b39 (patch)
tree5a3c35443e155b69a87456624ce458ee08a4ba08 /Documentation/trace
parent35a7f41cc6bb7013e344502b03c5583d04228bd3 (diff)
downloadlinux-197165d44925bd0fa892990851dee4d312a44b39.tar.bz2
powerpc/ftrace: add powerpc timebase as a trace clock source
Add a new powerpc-specific trace clock using the timebase register, similar to x86-tsc. This gives us - a fast, monotonic, hardware clock source for trace entries, and - a clock that can be used to correlate events across cpus as well as across hypervisor and guests. Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'Documentation/trace')
-rw-r--r--Documentation/trace/ftrace.txt5
1 files changed, 5 insertions, 0 deletions
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 7ddb1e319f84..87bb4aa6a6b9 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