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| author | Eiichi Tsukata <eiichi.tsukata.xh@hitachi.com> | 2013-04-11 20:25:16 +0900 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2013-05-03 13:58:09 +0200 |
| commit | e64dd5efb2c6d522a3bc9d096cd49a4e53f0ae10 (patch) | |
| tree | 91509cf96266b5c1589f76e8dd97d22c05186047 /docs/tracing.txt | |
| parent | 781e9545dbe54d2f0a530edbf48fd0ac1e77244c (diff) | |
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>
Diffstat (limited to 'docs/tracing.txt')
| -rw-r--r-- | docs/tracing.txt | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/docs/tracing.txt b/docs/tracing.txt index cf53c173ec..60ff9c5e6e 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> |