Thank you for taking the time to read about SCons. SCons is a next-generation software construction tool, or make tool--that is, a software utility for building. Full Changelog history) Downloads. All installers always install the latest version unless stated otherwise. Mac OS X installer; Windows installer (requires 32-bit or. How to download and install prebuilt OpenJDK packages JDK 8 Debian, Ubuntu, etc. On the command line, type: $ sudo apt-get install openjdk-8-jre. The openjdk-8-jre. LTTng is also worth a. If you do not have a programming background, you may wish to skip. What’s in this documentation? The LTTng Documentation is divided into the following sections: Nuts and bolts explains the. This guide contains information required to install Oracle Database 11g Release 1 (11.1) on various platforms of Linux. Ensure that you review information related to. Under Linux, there are two different implementations of Java that are available for use. Ubuntu and Arch let you easily install either implementation, while Fedora. LTTng project. An italic. Practical tips and notes are given throughout the document using the. Tip: Make sure you read the tips. Terminal boxes are used to show command lines: $. Command line as a regular user. Command line as a priviledged user. Command lines which you need to execute as a priviledged user start with. Other command lines start with the $. Acknowledgements. A few people made the online LTTng Documentation possible. Philippe Proulx wrote most of the content, created. He is the current maintainer. LTTng Documentation. Daniel U. Thibault, from the DRDC, wrote. The Linux Trace Toolkit Next Generation — A. Comprehensive User’s Guide (version 2. Core concepts and. Components of LTTng sections and for a few passages here. The entire Effici. OS team made essential reviews. We sincerely thank everyone who helped enhance the quality of this. LTTng 2. 9 bears the name Joann. A Berliner Weisse style. Tr. As its name suggests, the Linux Trace Toolkit: next. Linux systems and. So your first question might be. As the history of software engineering progressed and led to what. Linux—the authors of such. One major achievement in this field is, inarguably, the. GNU debugger (GDB). But even the best. A profiler is often the tool of choice to identify performance. Profiling is suitable to identify where performance is. The profiler outputs a profile, a statistical. However, a profiler won’t. Bottlenecks. might only occur when specific conditions are met, conditions that are. For a thorough investigation of software. This. is where tracing comes in handy. Tracing is a technique used to understand what goes on in a running. The software used for tracing is called a tracer. When recording. specific instrumentation points placed in the software source code. You. can trace user applications and the operating system at the same time. Tracing is often compared to logging. However, tracers and loggers are. Tracers are. designed to record much lower- level events that occur much more. Logging is more appropriate. Simply put. logging is one of the many use cases that can be satisfied with tracing. The list of recorded events inside a trace file can be read manually. Trace viewers and analyzers are specialized tools. In the end, this is what LTTng is: a powerful, open source set of. Linux kernel and user applications at the same time. The dtrace tool interprets. Linux kernel for further execution and collecting the outputted data. You can attach. such programs to tracepoints and KProbes thanks to a system call, and. VM register values, and e. BPF maps, to name. Its user. interface is a set of special files in sysfs. You write scripts, or chisels in. Lua and sysdig executes them while the system is. System. Tap converts the scripts to the C language, and then. Linux kernel modules which are loaded to produce. System. Tap’s primary user interface is the stap. It produces trace files in the. CTF format, a file format optimized. LTTng is the result of more than 1. The latter can create several tracing sessions, enable. LTTng can. record the traces on the file system or send them over the network, and. You can view the traces once tracing. Install LTTng now and. LTTng is a set of software components which interact to. Linux kernel and user applications, and. Those. components are bundled into the following packages: LTTng- tools: Libraries and command- line interface to. In the. following sections, we always provide the steps to install all three. You only need to install LTTng- modules if you intend to trace the. Linux kernel. You can set the PYTHON environment variable to the. Python interpreter for which to install the LTTng- UST Python. This can be useful to test. LTTng without installing it on your system. This is a short guide to get started quickly with LTTng kernel and user. Before you follow this guide, make sure to install. LTTng. This tutorial walks you through the steps to: Trace the Linux kernel. You can also trace the kernel. Unix user is a member of the. For example. load a website, or list the files of a directory. It is not * needed otherwise. Tracepoint provider name (required) * 2. Tracepoint name (required) * 3. The. program executes all tracepoint() instrumentation points and exits. The babeltrace command. Babeltrace project. However, more elaborate filters, such as keeping only. Moreover, reductions and even the. Fortunately, Babeltrace ships with Python 3 bindings which makes it easy. LTTng trace sequentially and compute the. The following script accepts an LTTng Linux kernel trace path as its. CPU 0 during the whole trace: top. Counterimportbabeltraceimportsysdeftop. Usage: python. 3 . You can. create a new tracing session with the lttng create command. Anything that you do when you control LTTng tracers happens within a. In particular, a tracing session. Has its own name. In the case of. the cash machine, a session lasts as long as your bank card is inside. The. tracing session mode dictates where to send it. The following modes. LTTng 2. 9. LTTng writes the traces to the file system of the machine being traced. Instead, you can request. LTTng to take a snapshot, that is, a copy of the. A tracing domain. There are currently five available tracing domains. JUL). You must specify a tracing domain when using some commands to avoid. For example, since all the domains support named tracepoints. Some features are reserved to specific tracing domains. Dynamic function. Linux kernel tracing domain, but support for other. You can create channels in the Linux kernel and user space. The other tracing domains have a single default. A channel is an object which is responsible for a set of ring buffers. When an LTTng. tracer emits an event, it can record it to one or more. The attributes of a channel determine what to do when. A channel is always associated to a tracing domain. The. java. util. logging (JUL), log. Python tracing domains each have. A channel also owns event rules. When an LTTng tracer emits. A channel has at least one ring buffer per CPU. LTTng always. records an event to the ring buffer associated to the CPU on which it. Two buffering schemes are available when you. Per- user buffering. Allocate one set of ring buffers—one per CPU—shared by all the. Unix user. However, the. The Linux kernel tracing domain has only one available buffering scheme. A consumer daemon. In an ideal world, sub- buffers are consumed faster than they are filled. In the real world. By design, LTTng is a non- blocking tracer: when no empty sub- buffer is. LTTng privileges performance over integrity; it aims at. When it comes to losing event records because no empty sub- buffer is. The. available event loss modes are. Drop the newest event records until a the tracer. In overwrite. mode, since LTTng 2. LTTng increments a count of lost sub- buffers when. In this mode. the exact number of lost event records in those lost sub- buffers is not. Trace analyses can use the trace’s saved discarded. There are a few ways to decrease your probability of losing event. Knowing this. the following list presents a few practical situations along with how. High event throughput: In general, prefer bigger sub- buffers to. For example, the average. LTTng kernel event record weights about 3. Thus, a. sub- buffer size of 1 Mi. B is considered big. The previous situations highlight the major trade- off between a few big. Assuming a. constant event throughput and using the overwrite mode, the two. Mi. B each: Expect a very low sub- buffer. Mi. B) are definitely lost. You can. set the switch timer period attribute when you. This attribute is also convenient when you use big sub- buffers to cope. By default, the LTTng tracers use a notification mechanism to signal a. When such. notifications must be avoided, for example in real- time applications. When the read timer. By default, trace files can grow as large as needed. You can set the. maximum size of each trace file that a channel writes when you. When the size of. LTTng creates. another file to contain the next event records. LTTng appends a file. If you set the trace file size attribute when you create a channel, the. LTTng creates is unlimited by. To limit them, you can also set a maximum number of trace. When the number of trace files reaches the channel’s fixed. This mechanism is. An event rule is a set of conditions which must be all satisfied. LTTng to record an occuring event. You set the conditions when you create an event rule. You always attach an event rule to channel when you create. When an event passes the conditions of an event rule, LTTng records it. The available conditions, as of LTTng 2. The event rule is enabled. This is why, without a filter, checking if an event. This is possible because the. In other words, without a dynamic filter, the tracer. Note that, for LTTng to record an event, the channel to. Logical path from an instrumentation point to an event record. Event, event record, or event rule? With so many similar terms, it’s easy to get confused. An event is the consequence of the execution of an instrumentation. Linux kernel KProbe. An event is said to occur at a specific. Different actions can be taken upon the occurrence of an event. An event record is the representation of an event in a sub- buffer. A. tracer is responsible for capturing the payload of an event, current. ID, and the event’s timestamp. LTTng. can append this sub- buffer to a trace file. An event rule is a set of conditions which must all be satisfied for. LTTng to record an occuring event. Events still occur without. LTTng does not record them. The second T in LTTng stands for toolkit: it would be wrong. LTTng a simple tool since it is composed of multiple. This section describes those components. LTTng ecosystem. The following diagram shows how the most important components of LTTng. Linux kernel, and you: Control and trace data paths between LTTng components.
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