_Linux Trace Toolkit: next generation_ is a modern toolkit for
tracing Linux systems and applications. So your first question might
rather be: **what is tracing?**
-
-As the history of software engineering progressed and led to what
-we now take for granted—complex, numerous and
-interdependent software applications running in parallel on
-sophisticated operating systems like Linux—the authors of such
-components, or software developers, began feeling a natural
-urge of having tools to ensure the robustness and good performance
-of their masterpieces.
-
-One major achievement in this field is, inarguably, the
-<a href="https://www.gnu.org/software/gdb/" class="ext">GNU debugger
-(GDB)</a>, which is an essential tool for developers to find and fix
-bugs. But even the best debugger won't help make your software run
-faster, and nowadays, faster softwares means either more work done by
-the same hardware, or cheaper hardware for the same work.
-
-A _profiler_ is often the tool of choice to identify performance
-bottleneck. Profiling is suitable to identify _where_ performance is
-lost in a given software; the profiler outputs a profile, a
-statistical summary of observed events, which you may use to know
-which functions took the most time to execute. However, a profiler
-won't report _why_ some identified functions are the bottleneck.
-Also, bottlenecks might only occur when specific conditions are met.
-For a thorough investigation of software performance issues, a history
-of execution, with historical values of chosen variables, is
-essential. This is where tracing comes in handy.
-
-_Tracing_ is a technique used to understand what goes on in a running
-software system. The software used for tracing is called a _tracer_,
-which is conceptually similar to a tape recorder. When recording,
-specific points placed in the software source code generate events
-that are saved on a giant tape: a _trace_ file. Both user applications
-and the operating system may be traced at the same time, opening the
-possibility of resolving a wide range of problems that are otherwise
-extremely challenging.
-
-Tracing is often compared to _logging_. However, tracers and loggers
-are two different tools, serving two different purposes. Tracers are
-designed to record much lower-level events that occur much more
-frequently than log messages, often in the thousands per second range,
-with very little execution overhead. Logging is more appropriate for
-very high-level analysis of less frequent events: user accesses,
-exceptional conditions (e.g., errors, warnings), database
-transactions, instant messaging communications, etc. More formally,
-logging is one of several use cases that can be accomplished with
-tracing.
-
-The list of recorded events inside a trace file may be read manually
-like a log file for the maximum level of detail, but it is generally
-much more interesting to perform application-specific analyses to
-produce reduced statistics and graphs that are useful to resolve a
-given problem. Trace viewers and analysers are specialized tools which
-achieve this.
-
-So, in the end, this is what LTTng is: a powerful, open source set of
-tools to trace the Linux kernel and user applications. LTTng is
-composed of several components actively maintained and developed by
-its community.
-
-Excluding proprietary solutions, a few competing software tracers
-exist for Linux.
-<a href="https://www.kernel.org/doc/Documentation/trace/ftrace.txt" class="ext">ftrace</a>
-is the de facto function tracer of the Linux kernel.
-<a href="http://linux.die.net/man/1/strace" class="ext">strace</a>
-is able to record all system calls made by a user process.
-<a href="https://sourceware.org/systemtap/" class="ext">SystemTap</a>
-is a Linux kernel and user space tracer which uses custom user scripts
-to produce plain text traces.
-<a href="http://www.sysdig.org/" class="ext">sysdig</a>
-also uses scripts, written in Lua, to trace and analyze the Linux
-kernel.
-
-The main distinctive features of LTTng is that it produces correlated
-kernel and user space traces, as well as doing so with the lowest
-overhead amongst other solutions. It produces trace files in the
-<a href="http://www.efficios.com/ctf" class="ext"><abbr title="Common Trace Format">CTF</abbr></a>
-format, an optimized file format for production and analyses of
-multi-gigabyte data. LTTng is the result of close to 10 years of
-active development by a community of passionate developers. It is
-currently available on all major desktop and embedded Linux
-distributions.
-
-The main interface for tracing control is a single command line tool
-named `lttng`. The latter can create several tracing sessions,
-enable/disable events on the fly, filter them efficiently with custom
-user expressions, start/stop tracing and do much more. Traces can be
-recorded on disk or sent over the network, kept totally or partially,
-and viewed once tracing is inactive or in real-time.
-
-[Install LTTng now](#doc-installing-lttng) and start tracing!
projects / lttng-docs.git / blobdiff