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authorEiichi Tsukata <eiichi.tsukata.xh@hitachi.com>2013-04-11 20:25:16 +0900
committerStefan Hajnoczi <stefanha@redhat.com>2013-05-03 13:58:09 +0200
commite64dd5efb2c6d522a3bc9d096cd49a4e53f0ae10 (patch)
tree91509cf96266b5c1589f76e8dd97d22c05186047
parent781e9545dbe54d2f0a530edbf48fd0ac1e77244c (diff)
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trace: document ftrace backend
Add documentation of ftrace backend. Signed-off-by: Eiichi Tsukata <eiichi.tsukata.xh@hitachi.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
-rw-r--r--docs/tracing.txt16
1 files changed, 16 insertions, 0 deletions
diff --git a/docs/tracing.txt b/docs/tracing.txt
index cf53c17..60ff9c5 100644
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -175,6 +175,22 @@ unless you have specific needs for more advanced backends.
The "simple" backend currently does not capture string arguments, it simply
records the char* pointer value instead of the string that is pointed to.
+=== Ftrace ===
+
+The "ftrace" backend writes trace data to ftrace marker. This effectively
+sends trace events to ftrace ring buffer, and you can compare qemu trace
+data and kernel(especially kvm.ko when using KVM) trace data.
+
+if you use KVM, enable kvm events in ftrace:
+
+ # echo 1 > /sys/kernel/debug/tracing/events/kvm/enable
+
+After running qemu by root user, you can get the trace:
+
+ # cat /sys/kernel/debug/tracing/trace
+
+Restriction: "ftrace" backend is restricted to Linux only.
+
==== Monitor commands ====
* trace-file on|off|flush|set <path>