libguestfs User-Space Markers
libguestfs includes support for SystemTap user-space markers and are enabled in current versions of Fedora and Red Hat Enterprise Linux 7. The markers allow SystemTap to probe various steps in libguestfs operation. Below is an listing of the libguestfs events available on RHEL7:
$ stap -L 'process("/usr/lib*/libguestfs.so.*").mark("*")'
process("/usr/lib64/libguestfs.so.0.471.0").mark("launch_build_appliance_end")
process("/usr/lib64/libguestfs.so.0.471.0").mark("launch_build_appliance_start")
process("/usr/lib64/libguestfs.so.0.471.0").mark("launch_build_libvirt_appliance_end")
process("/usr/lib64/libguestfs.so.0.471.0").mark("launch_build_libvirt_appliance_start")
process("/usr/lib64/libguestfs.so.0.471.0").mark("launch_build_libvirt_qcow2_overlay_end")
process("/usr/lib64/libguestfs.so.0.471.0").mark("launch_end")
process("/usr/lib64/libguestfs.so.0.471.0").mark("launch_libvirt_end")
process("/usr/lib64/libguestfs.so.0.471.0").mark("launch_libvirt_start")
process("/usr/lib64/libguestfs.so.0.471.0").mark("launch_run_qemu")
process("/usr/lib64/libguestfs.so.0.471.0").mark("launch_start")
Using libguestfs User-Space Markers
To use the libguestfs user-space markers on Fedora you will need:
- RPMs:
- libguestfs
- libguestfs-tools-c
- systemtap-client
- Membership to the stapdev group (or root access)
Examples and Demonstrations of Markers
The following libguestfs_log.stp script will log each time one of the libguestfs user-space markers is encountered.
global start_time, prev;
function display_time () {
now = gettimeofday_us ()
delta = (prev > 0 ) ? now - prev : 0
printf ("%18d (+%10d): ", now - start_time, delta)
prev = now
}
probe begin {
start_time = gettimeofday_us ()
prev = 0
printf ("%-18s (+%10s): %s\n", "# time_usec",
"delta usec", "event")
}
probe process("/usr/lib*/libguestfs.so.0*").mark("*")
{
display_time()
printf ("%s\n", $$name)
}In one terminal window start the script. Once the header is printed indicating the script is started in another window run guestfish -N fs :
$ stap libguestfs_log.stp
# time_usec (+delta usec): event
3275625 (+ 0): launch_start
3275683 (+ 58): launch_libvirt_start
3554578 (+ 278895): launch_build_libvirt_appliance_start
3563691 (+ 9113): launch_build_libvirt_appliance_end
3569845 (+ 6154): launch_build_libvirt_qcow2_overlay_end
4795301 (+ 1225456): launch_libvirt_end
^C$