[tip:tracing/core] tracing: Add documentation for the power tracer

[Theodore Ts'o]

Commit-ID:  f7a3b3845cdfa4d6383b74139392ff5c259531fc
Gitweb:     http://git.kernel.org/tip/f7a3b3845cdfa4d6383b74139392ff5c259531fc
Author:     Theodore Ts'o <tytso@xxxxxxx>
AuthorDate: Sat, 11 Apr 2009 15:51:19 -0400
Committer:  Ingo Molnar <mingo@xxxxxxx>
CommitDate: Sun, 12 Apr 2009 11:23:49 +0200

tracing: Add documentation for the power tracer

Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Acked-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Steven Rostedt <srostedt@xxxxxxxxxx>
LKML-Reference: <1239479479-2603-4-git-send-email-tytso@xxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
 Documentation/trace/power.txt |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/Documentation/trace/power.txt b/Documentation/trace/power.txt
new file mode 100644
index 0000000..9c584ff
--- /dev/null
+++ b/Documentation/trace/power.txt
@@ -0,0 +1,17 @@
+The power trace collects detailed information about C-state and P-state
+transitions, instead of just looking at the high-level "average"
+information.
+
+There is a helper script found in scrips/tracing/power.pl in the kernel
+sources which can be used to parse this information and create a
+Scalable Vector Graphics (SVG) picture from the trace data.
+
+To use this tracer:
+
+	echo 0 > /sys/kernel/debug/tracing/tracing_enabled
+	echo power > /sys/kernel/debug/tracing/current_tracer
+	echo 1 > /sys/kernel/debug/tracing/tracing_enabled
+	sleep 1
+	echo 0 > /sys/kernel/debug/tracing/tracing_enabled
+	cat /sys/kernel/debug/tracing/trace | \
+		perl scripts/tracing/power.pl > out.sv
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