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[Qemu-devel] [PATCH 2/2] trace: document frace backend
From: |
Eiichi Tsukata |
Subject: |
[Qemu-devel] [PATCH 2/2] trace: document frace backend |
Date: |
Wed, 3 Apr 2013 12:41:09 +0900 |
Add documentation of ftrace backend.
Signed-off-by: Eiichi Tsukata <address@hidden>
---
docs/tracing.txt | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
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>
--
1.8.1.4