Caliper

by LLNL

LLNL / Caliper

Caliper is an instrumentation and performance profiling library

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Caliper: A Performance Analysis Toolbox in a Library

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Caliper is a program instrumentation and performance measurement framework. It is a performance analysis toolbox in a library, allowing one to bake performance analysis capabilities directly into applications and activate them at runtime.

Caliper can be used for lightweight always-on profiling or advanced performance engineering use cases, such as tracing, monitoring, and auto-tuning. It is primarily aimed at HPC applications, but works for any C/C++/Fortran program on Unix/Linux.

Features include:

  • Low-overhead source-code annotation API
  • Configuration API to control performance measurements from within an application
  • Flexible key:value data model: capture application-specific features for performance analysis
  • Fully threadsafe implementation, support for parallel programming models like MPI
  • Synchronous (event-based) and asynchronous (sampling) performance data collection
  • Trace and profile recording
  • Connection to third-party tools, e.g. NVidia NVProf or Intel(R) VTune(tm)
  • Measurement and profiling functionality such as timers, PAPI hardware counters, and Linux perf_events
  • Memory allocation annotations: associate performance measurements with named memory regions

Documentation

Extensive documentation is available here: https://llnl.github.io/Caliper/

Usage examples of the C++, C, and Fortran annotation and ConfigManager APIs are provided in the examples directory.

See the "Getting started" section below for a brief tutorial.

Building and installing

Building and installing Caliper requires cmake 3.1+ and a current C++11-compatible Compiler. Clone Caliper from github and proceed as follows:

 $ git clone https://github.com/LLNL/Caliper.git
 $ cd Caliper
 $ mkdir build && cd build
 $ cmake -DCMAKE_INSTALL_PREFIX= \
     -DCMAKE_C_COMPILER= \
     -DCMAKE_CXX_COMPILER= \
     ..
 $ make
 $ make install

See the "Build and install" section in the documentation for further information.

Getting started

Typically, we integrate Caliper into a program by marking source-code sections of interest with descriptive annotations. Performance measurements, trace or profile collection, and reporting functionality can then be enabled with runtime configuration options. Alternatively, third-party tools can connect to Caliper and access information provided by the source-code annotations.

Source-code annotations

Caliper source-code annotations let us associate performance measurements with user-defined, high-level context information. We can also trigger user-defined actions at the instrumentation points, e.g. to measure the time spent in annotated regions. Measurement actions can be defined at runtime and are disabled by default; generally, the source-code annotations are lightweight enough to be left in production code.

The annotation APIs are available for C, C++, and Fortran. There are high-level annotation macros for common scenarios such as marking functions, loops, or sections of source-code. In addition, users can export arbitrary key:value pairs to express application-specific concepts.

The following example marks "initialization" and "main loop" phases in a C++ code, and exports the main loop's current iteration counter using the high-level annotation macros:

#include 

int main(int argc, char* argv[]) { // Mark this function CALI_CXX_MARK_FUNCTION;

// Mark the "intialization" phase
CALI_MARK_BEGIN("initialization");
int count = 4;
double t = 0.0, delta_t = 1e-6;
CALI_MARK_END("initialization");

// Mark the loop
CALI_CXX_MARK_LOOP_BEGIN(mainloop, "main loop");

for (int i = 0; i < count; ++i) {
    // Mark each loop iteration
    CALI_CXX_MARK_LOOP_ITERATION(mainloop, i);

    // A Caliper snapshot taken at this point will contain
    // { "function"="main", "loop"="main loop", "iteration#main loop"=<i> }

    // ...
}

CALI_CXX_MARK_LOOP_END(mainloop);

}

Linking the Caliper library

To use Caliper, add annotation statements to your program and link it against the Caliper library. Programs must be linked with the Caliper runtime (libcaliper.so), as shown in the example link command:

g++ -o app app.o -L/lib64 -lcaliper

Recording performance data

Performance measuremens can be controlled most conveniently via the ConfigManager API. The ConfigManager covers many common use cases, such as recording traces or printing time reports. For custom analysis tasks or when not using the ConfigManager API, Caliper can be configured manually by setting configuration variables via the environment or in config files.

ConfigManager API

With the C++ ConfigManager API, built-in performance measurement and reporting configurations can be activated within a program using a short configuration string. This configuration string can be hard-coded in the program or provided by the user in some form, e.g. as a command-line parameter or in the programs's configuration file.

To use the ConfigManager API, create a

cali::ConfigManager
object, add a configuration string with
add()
, start the requested configuration channels with
start()
, and trigger output with
flush()
:
#include 
// ...
cali::ConfigManager mgr;
mgr.add("runtime-report");
// ...
mgr.start(); // start requested performance measurement channels
// ... (program execution)
mgr.flush(); // write performance results

A complete code example where users can provide a configuration string on the command line is here. Built-in configs include

  • runtime-report: Prints a time profile for annotated code regions.
  • event-trace: Records a trace of region begin/end events.

Complete documentation on the ConfigManager configurations can be found here.

Manual configuration through environment variables

The ConfigManager API is not required to run Caliper - performance measurements can also be configured with environment variables or a config file. For starters, there are a set of pre-defined configuration profiles that can be activated with the

CALI_CONFIG_PROFILE
environment variable. For example, the
runtime-report
configuration profile prints the total time (in microseconds) spent in each code path based on the nesting of annotated code regions:
$ CALI_CONFIG_PROFILE=runtime-report ./examples/apps/cxx-example
Path         Inclusive time (usec) Exclusive time (usec) Time %
main                     38.000000             20.000000   52.6
  main loop               8.000000              8.000000   21.1
  init                   10.000000             10.000000   26.3

The example shows Caliper output for the

runtime-report
configuration profile for the source-code annotation example above.

For complete control, users can select and configure Caliper services manually. For example, this configuration records an event trace recording all enter and leave events for annotated code regions:

$ CALI_SERVICES_ENABLE=event,recorder,timestamp,trace ./examples/apps/cxx-example
== CALIPER: Registered event trigger service
== CALIPER: Registered recorder service
== CALIPER: Registered timestamp service
== CALIPER: Registered trace service
== CALIPER: Initialized
== CALIPER: Flushing Caliper data
== CALIPER: Trace: Flushed 14 snapshots.
== CALIPER: Recorder: Wrote 71 records.

The trace data is stored in a

.cali
file in a text-based Caliper-specific file format. Use the
cali-query
tool to filter, aggregate, or print the recorded data. Here, we use
cali-query
to print the recorded trace data in a human-readable json format:
$ ls *.cali
171120-181836_40337_7LOlCN5RchWV.cali
$ cali-query 171120-181836_40337_7LOlCN5RchWV.cali -q "SELECT * FORMAT json(pretty)"
[
{
        "event.begin#function":"main"
},
{
        "event.begin#annotation":"init",
        "function":"main"
},
{
        "event.end#annotation":"init",
        "annotation":"init",
        "function":"main",
        "time.inclusive.duration":14
},
...

More information can be found in the Caliper documentation.

Authors

Caliper was created by David Boehme, [email protected]

A complete list of contributors is available on GitHub.

Major contributors include:

Citing Caliper

To reference Caliper in a publication, please cite the following paper:

Release

Caliper is released under a BSD 3-clause license. See LICENSE for details.

LLNL-CODE-678900

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