SystemTap Tapset Reference Manual William Cohen
wcohen@redhat.com
2008, 2009 Red Hat, Inc. 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. Introduction 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.
Tapset Name Format 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.
Context Functions The context functions provide additional information about the where the event occurred. These functions can provide information such as a backtrace where the event occured and the current register values for the processor. !Itapset/context.stp !Itapset/context-symbols.stp !Itapset/context-unwind.stp Timestamp Functions Each timestamp function returns a value to indicate when the function is executed. Thus, these returned values can be used to indicate when an event occurs, provide an ordering for events, or compute the amount of time elapsed between to time stamps. !Itapset/timestamp.stp Memory Tapset !Itapset/memory.stp IO Scheduler Tapset This family of probe points is used to probe the IO scheduler activities. It contains the following probe points: !Itapset/ioscheduler.stp SCSI Tapset This family of probe points is used to probe the SCSI activities. It contains the following probe points: !Itapset/scsi.stp Networking Tapset This family of probe points is used to probe the activities of network device. !Itapset/networking.stp Socket Tapset This family of probe points is used to probe socket activities. It contains the following probe points: !Itapset/socket.stp TCP Tapset This family of probe points is used to probe TCP layer activities. It contains the following probe points: !Itapset/tcp.stp UDP Tapset This family of probe points is used to probe UDP layer activities. It contains the following probe points: !Itapset/udp.stp Process Tapset This family of probe points is used to probe the process activities. It contains the following probe points: !Itapset/process.stp Signal Tapset This family of probe points is used to probe signal activities. It contains the following probe points: !Itapset/signal.stp