Chapter 11. Compiler and Tools

SystemTap Updated to Version 1.8

SystemTap is a tracing and probing tool that allows users to study and monitor the activities of the operating system (particularly, the kernel) in fine detail. It provides information similar to the output of tools like netstat, ps, top, and iostat; however, SystemTap is designed to provide more filtering and analysis options for collected information.
The systemtap package in Red Hat Enterprise Linux 6.4 has been upgraded to upstream version 1.8, which provides a number of bug fixes and enhancements:
  • The @var syntax is now an alternative language syntax for accessing DWARF variables in uprobe and kprobe handlers (process, kernel, module).
  • SystemTap now mangles local variables to avoid collisions with C headers included by tapsets.
  • The SystemTap compile-server and client now support IPv6 networks, for hosts listed in DNS or mDNS.
  • The SystemTap runtime (staprun) now accepts a -T timeout option to allow less frequent wake-ups to poll for low-throughput output from scripts.
  • The SystemTap script translator driver (stap) now provides the following resource limit options:
    --rlimit-as=NUM
    --rlimit-cpu=NUM
    --rlimit-nproc=NUM
    --rlimit-stack=NUM
    --rlimit-fsize=NUM
    
  • SystemTap modules are now smaller and compile faster. The modules' debuginfo is now suppressed by default.
  • Bug CVE-2012-0875 (kernel panic when processing malformed DWARF unwind data) is now fixed.

The lscpu and chcpu Utilities

The lscpu utility, which displays detailed information about the available CPUs has been updated to include numerous new features. Also, a new utility, chcpu, has been added, which allows you to change the CPU state (online/offline, standby/active, and other states), disable and enable CPUs, and configure specified CPUs.
For more information about these utilities, refer to the lscpu(1) and chcpu(8) man pages.