On Thu, Aug 06, 2020 at 02:34:02PM +0800, Han Han wrote: > Signed-off-by: Han Han <hhan@xxxxxxxxxx> > --- > docs/kbase.rst | 3 ++ > docs/kbase/meson.build | 1 + > docs/kbase/systemtap.rst | 113 +++++++++++++++++++++++++++++++++++++++ > 3 files changed, 117 insertions(+) > create mode 100644 docs/kbase/systemtap.rst > > diff --git a/docs/kbase.rst b/docs/kbase.rst > index 78daaa5989..d8bff5d41e 100644 > --- a/docs/kbase.rst > +++ b/docs/kbase.rst > @@ -36,6 +36,9 @@ Knowledge base > Examination of the security protections used for QEMU and how they need > configuring to allow use of QEMU passthrough with host files/devices. > > + `Systemtap <kbase/systemtap.html>`__ > + Explanation of how to use systemtap for libvirt tracing. > + > `Virtio-FS <kbase/virtiofs.html>`__ > Share a filesystem between the guest and the host > > diff --git a/docs/kbase/meson.build b/docs/kbase/meson.build > index d7f254e163..ca032a4b9b 100644 > --- a/docs/kbase/meson.build > +++ b/docs/kbase/meson.build > @@ -13,6 +13,7 @@ docs_kbase_files = [ > 'rpm-deployment', > 's390_protected_virt', > 'secureusage', > + 'systemtap', > 'virtiofs', > ] > > diff --git a/docs/kbase/systemtap.rst b/docs/kbase/systemtap.rst > new file mode 100644 > index 0000000000..34420efbb2 > --- /dev/null > +++ b/docs/kbase/systemtap.rst > @@ -0,0 +1,113 @@ > +======================= > +Systemtap of Libvirt > +======================= The "===" are too long here and all the other headings. > + > +.. contents:: > + > +`Systemtap <https://sourceware.org/systemtap/>`__ is a scripting > +language and tool for dynamically probing or tracing in Linux kernel > +space or user space. This page is about the usage of systemtap > +in libvirt tracing. > + > +Preparation > +=================== > + > +Libvirt > +------------------------- > + > +Libvirt should be configured with the systemtap option to support libvirt > +probing events in systemtap. > + > +For libvirt before **6.7.0**, it can be configured by: > + > +:: > + > + mkdir build > + cd build > + ../configure --with-dtrace > + > +For libvirt **6.7.0** or later, configure it by the ``meson`` (seeing > +`libvirt compiling <https://libvirt.org/compiling.html>`__): > + > +:: > + > + meson build -Ddtrace=enabled > + > +For the libvirt binaries installed by the package manager like ``dnf`` or > +``apt``, if libvirt systemtap tapset ``/usr/share/systemtap/tapset/libvirt_*`` > +exists, it means the libvirt enables the systemtap feature. > + > +Systemtap > +------------------------ > + > +For most of linux distributions, execute ``stap-prep`` by root to prepare the > +environment for systemtap after installing the systemtap. If your distribution > +doesn't have ``stap-prep``, install the ``kernel debuginfo`` packages manually. > + > +After these above, run this test command to confirm the systemtap works well: > + > +:: > + > + stap -e 'probe oneshot{ printf("hello world\n")}' > + > + > +Tracing events > +======================= > + > +The libvirt systemtap tracing events are defined in tapset > +``/usr/share/systemtap/tapset/libvirt_*``. Libvirt support these type of tracing > +events: ``dbus``, ``event_glib``, ``object``, ``qemu``, ``rpc``. > + > +List all tracing events in libvirt: > + > +:: > + > + grep 'probe libvirt.[a-z_0-9.]*' /usr/share/systemtap/tapset/libvirt_* -o|cut -f 2 -d : > + > + > +Tracing examples > +================== > + > +Here is an example of the systemtap script to trace the QMP messages sent from libvirtd > +daemon to the qemu process. > +``qmp.stp``: > + > +:: > + > + probe begin > + { > + printf("Start tracing\n") > + } > + probe libvirt.qemu.monitor_send_msg > + { > + printf("QMPs: %s", msg); > + } > + > +Then run the systemtap script attaching to the libvirtd process: > + > +:: > + > + stap qmp.stp -x `pidof libvirtd` > + > + > +To trace a libvirtd started from command line, use the option ``-c`` > + > +:: > + > + stap qmp.stp -c "/usr/sbin/libvirtd" > + > + > +Then after seeing the welcome message "Start tracing" from systemtap, then execute a virsh > +command associated with QMP, for example ``virsh domstats``. Then get the QMP tracing logs > +from systemtap. For example, the result from ``virsh domstats`` > + > +:: > + > + QMPs: {"execute":"query-balloon","id":"libvirt-393"} > + QMPs: {"execute":"qom-get","arguments":{"path":"/machine/peripheral/balloon0","property":"guest-stats"},"id":"libvirt-394"} > + QMPs: {"execute":"query-blockstats","id":"libvirt-395"} > + QMPs: {"execute":"query-named-block-nodes","id":"libvirt-396"} > + QMPs: {"execute":"query-iothreads","id":"libvirt-397"} > + > +For more examples of libvirt systemtap scripts, see the scripts in ``/usr/share/doc/libvirt-docs/examples/systemtap`` > +For more details of systemtap language, see `document of systemtap <https://sourceware.org/systemtap/documentation.html>`__ > -- Reviewed-by: Daniel P. Berrangé <berrange@xxxxxxxxxx> and pushed after trimming the heading markers Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
