2008-2009 Red Hat, Inc. and others SystemTap Hackers This documentation is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 2 as published by the Free Software Foundation. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA For more details see the file COPYING in the source distribution of Linux. SystemTap provides free software (GPL) infrastructure to simplify the gathering of information about the running Linux system. This assists diagnosis of a performance or functional problem. SystemTap eliminates the need for the developer to go through the tedious and disruptive instrument, recompile, install, and reboot sequence that may be otherwise required to collect data. SystemTap provides a simple command line interface and scripting language for writing instrumentation for a live running kernel. The instrumentation makes extensive use of the probe points and functions provided in the tapset library. This document describes the various probe points and functions.

In this guide, tapset definitions appear in the following format: name:return (parameters) definition The return field specifies what data type the tapset extracts and returns from the kernel during a probe (and thus, returns). Tapsets use 2 data types for return: long (tapset extracts and returns an integer) and string (tapset extracts and returns a string). In some cases, tapsets do not have a return value. This simply means that the tapset does not extract anything from the kernel. This is common among asynchronous events such as timers, exit functions, and print functions.

The context functions provide additional information about where an event occurred. These functions can provide information such as a backtrace to where the event occurred and the current register values for the processor. !Itapset/context.stp !Itapset/context-symbols.stp !Itapset/ucontext-symbols.stp !Itapset/context-unwind.stp !Itapset/ucontext-unwind.stp Each timestamp function returns a value to indicate when a function is executed. These returned values can then be used to indicate when an event occurred, provide an ordering for events, or compute the amount of time elapsed between two time stamps. !Itapset/timestamp.stp This family of probe points is used to probe memory-related events or query the memory usage of the current process. It contains the following probe points: !Itapset/memory.stp !Itapset/proc_mem.stp This tapset defines utility functions to query time related properties of the current tasks, translate those in miliseconds and human readable strings. !Itapset/task_time.stp This family of probe points is used to probe IO scheduler activities. It contains the following probe points: !Itapset/ioscheduler.stp This family of probe points is used to probe SCSI activities. It contains the following probe points: !Itapset/scsi.stp This family of probe points is used to probe TTY (Teletype) activities. It contains the following probe points: !Itapset/tty.stp This family of probe points is used to probe the activities of the network device and protocol layers. !Itapset/networking.stp !Itapset/tcp.stp !Itapset/udp.stp !Itapset/ip.stp This family of probe points is used to probe socket activities. It contains the following probe points: !Itapset/socket.stp This family of probe points is used to probe process-related activities. It contains the following probe points: !Itapset/kprocess.stp This family of probe points is used to probe signal activities. It contains the following probe points: !Itapset/signal.stp This family of functions is used to map kernel VFS directory entry pointers to file or full path names. !Itapset/dentry.stp This family of functions is used to send simple message strings to various destinations. !Itapset/logging.stp These functions deal with random number generation. !Itapset/random.stp