Tracing KVM with ftrace
=======================

Doc
---

http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/trace/tracepoint-analysis.txt?id=HEAD
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/trace/ftrace.txt?id=HEAD
http://lwn.net/Articles/370423/
http://lwn.net/Articles/365835/
http://lwn.net/Articles/366796/

Tracing L2 guest
----------------

  $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/trace-cmd.git trace-cmd

  # Build and Install
  $ make && sudo make-install

  # Optionally
  $ sudo yum install asciidoc -y
  $ sudo make install_doc 

  # To find all possible events
  $ sudo find /sys/kernel/debug/tracing/events -type d 

  # Let's find what's relevant for KVM 
  $ sudo find /sys/kernel/debug/tracing/events -type d 
  /sys/kernel/debug/tracing/events/kvmmmu

  # Start Trace command with kvmmmu
  $ trace-cmd record -b 2000 -e kvmmmu
  /sys/kernel/debug/tracing/events/kvmmmu/filter
  /sys/kernel/debug/tracing/events/*/kvmmmu/filter
  Hit Ctrl^C to stop recording

  (trace-cmd will wait)

  Run your workload, then stop trace-cmd with ctrl-C. trace-cmd will write a trace.dat file.

  # Start L2 guest 
  $ virsh start nguest-01 --console

  After a minute or two, ctl-C the trace-cmd,

  # Generate the report
  $ trace-cmd report

More tracing
------------

This works:

      $ trace-cmd record -e kvm:kvm_exit -e kvm:kvm_entry \
            -e kvm:kvm_nested_vmexit -e kvm:kvm_nested_vmrun


Tips (Thanks Paolo Bonzini)
--------------------------

    $ trace-cmd record -e kvm/* qemu-system-x86_64 [. . .]

    $ trace-cmd record -e kvm -e kvmmu -P 18697"