SystemTap 2.4 has been released today for effective information gathering and software diagnostics on Linux systems. SystemTap 2.4 provides smarter error reporting, support for virtual machine probing using libvirt, and other new functionality.
Some of the SystemTap 2.4 features include better suggestions in many of the semantic errors, smarter error reporting with regards to duplicate errors, support for probing inside virtual machines using libvirt and unix schemes, scripting language work, improved memory allocation, and run-time improvements.
More details on SystemTap 2.4 can be found via the release announcement
and project site