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Kokkos Tools

Kokkos Tools provide a set of light-weight of profiling and debugging utilities, which interface with instrumentation hooks built directly into the Kokkos runtime. Compared to 3rd party tools these tools can provide much cleaner, context-specific information: in particular, they allow kernel-centric analysis and they use labels provided to Kokkos constructs (kernel launches and views).

Under most circumstances, the profiling hooks are compiled into Kokkos executables by default assuming that the profiling hooks' version is compatible with the tools' version. No recompilation or changes to your build procedures are required.

Note: Kokkos must be configured with Kokkos_ENABLE_LIBDL=ON to load profiling hooks dynamically. This is the default for most cases anyway.

General Usage

To use one of the tools you have to compile it, which will generate a dynamic library. Before executing the Kokkos application you then have to set the environment variable KOKKOS_TOOLS_LIBS to point to the dynamic library e.g. in the bash shell:

export KOKKOS_TOOLS_LIBS=${HOME}/kokkos-tools/src/tools/memory-events/kp_memory_event.so

Many of the tools will produce an output file that uses the hostname as well as the process id as part of the filename.

Explicit Instrumentation

One can explicitly add instrumentation to a library or an application. Currently, the only hooks intended for explicit programmer use are the Region related hooks. These use a push/pop model to mark coarser regions in your code.

void foo() {
   Kokkos::Profiling::pushRegion("foo");
   bar();
   stool();
   Kokkos::Profiling::popRegion();
}

Tools

The following provides an overview of the tools available in the set of Kokkos Tools. Click on each Kokkos Tools name to see more details about the tool via the Kokkos Tools Wiki.

Utilities

  • KernelFilter:

    A tool which is used in conjunction with analysis tools, to restrict them to a subset of the application.

Memory Analysis

  • MemoryHighWater:

    This tool outputs the high water mark of memory usage of the application. The high water mark of memory usage is the highest amount of memory that is being utilized during the application's execution.

  • MemoryUsage:

    Generates a per Memory Space timeline of memory utilization.

  • MemoryEvents:

    Tool to track memory events such as allocation and deallocation. It also provides the information of the MemoryUsage tool.

Kernel Inspection

  • SimpleKernelTimer

    Captures basic timing information for Kernels.

  • KernelLogger

    Prints Kokkos Kernel and Region events during runtime.

  • Functor Size

    Prints information about the size of the functor objects passed to Kokkos parallel regions.

3rd Party Profiling Tool Hooks

  • VTuneConnector:

    Provides Kokkos Kernel Names to VTune, so that analysis can be performed on a per kernel base.

  • VTuneFocusedConnector:

    Like VTuneConnector but turns profiling off outside of kernels. Should be used in conjunction with the KernelFilter tool.

  • NVTXConnector:

    Provides Kokkos Kernel Names to NVTX, so that analysis can be performed on a per kernel base.

  • Timemory:

    Modular connector for accumulating timing, memory usage, hardware counters, and other various metrics. Supports controlling VTune, CUDA profilers, and TAU + kernel name forwarding to VTune, NVTX, TAU, Caliper, and LIKWID.

    If you need to write your own plug-in, this provides a straight-forward API to writing the plug-in.

    Defining a timemory component will enable your plug-in to output to stdout, text, and JSON, accumulate statistics, and utilize various portable function calls for common needs w.r.t. timers, resource usage, etc.

Building Kokkos Tools

Use either CMake or Makefile to build Kokkos Tools.

Using cmake

  1. create a build directory in Kokkos Tools, e.g., type mkdir myBuild; cd myBuild
  2. To configure the Type ccmake .. for any options you would like to enable/disable.
  3. To compile, type make
  4. To install, type make install

Using make

To build with make, simply type make within each subdirectory of Kokkos Tools.

Building using make is currently recommended. Eventually, the preferred method of building will be cmake.

Running a Kokkos-based Application with a tool

Given your tool shared library <name_of_tool_shared_library>.so (which contains kokkos profiling callback functions) and an application executable called yourApplication.exe, type:

export KOKKOS_TOOLS_LIBS=${YOUR_KOKKOS_TOOLS_DIR}/<name_of_tool_shared_lib>; ./yourApplication.exe

Tutorial

A tutorial on Kokkos Tools can be found here: https://github.com/kokkos/kokkos-tutorials/blob/main/LectureSeries/KokkosTutorial_07_Tools.pdf

Contact

Acknowledgement

Special thanks to David Poliakoff on earlier work on Kokkos Tools development.