Dynamic Filtering Plugin for Score-P

This plugin filters instrumentation calls from a binary instrumented with Score-P. Filtered calls are overwritten with NOPs to minimize overhead.

This work is part of Philipp Trommlers bachelor's thesis. Results will be made available as soon as they're ready.

Compilation and Installation

Prerequisites

To compile this plugin, you need:

• C compiler (with --std=c11 support)

• CMake

• Score-P installation

• libunwind

Building

1. Create a build directory

    mkdir build
    cd build
   

2. Invoke CMake

    cmake ..
   

   If your Score-P installation is in a non-standard path, you have to manually pass that path to CMake:

    cmake .. -DSCOREP_CONFIG=<PATH_TO_YOUR_SCOREP_ROOT_DIR>/bin/scorep-config
   

   If you want to build the plugin with a more verbose debug output, you can invoke CMake as follows:

    cmake .. -DBUILD_DEBUG=on
   

   This plugin defaults to the identity function as the hash for uthash as this has proven slightly faster than the built-ins of uthash. However, if you experience performance issues during hash table access, you can choose one of the built-in functions as mentioned here, e.g.:

    cmake .. -DHASH_FUNCTION=HASH_JEN
   

   By default, only the first 512 created threads are observed by the plugin. If your program uses more than 512 threads and you want all of them to be observed, you can increase this maximum by passing a higher value as MAX_THREAD_CNT to CMake. You can also lower the number of observed threads which may lead to a slightly lower overhead (but may also change the results).

    cmake .. -DMAX_THREAD_CNT=1024
   

3. Invoke make

    make
   

4. Copy the resulting library to a directory listed in LD_LIBRARY_PATH or add the current path to LD_LIBRARY_PATH with

    export LD_LIBRARY_PATH=`pwd`:$LD_LIBRARY_PATH
   

Usage

In order to use this plugin, you have to add it to the SCOREP_SUBSTRATES_PLUGINS environment variable.

export SCOREP_SUBSTRATE_PLUGINS="dynamic_filtering"

The configuration of the plugin is done via environment variables.

Environment variables

• SCOREP_SUBSTRATE_DYNAMIC_FILTERING_METHOD (string)

  Specifies the metric used by the plugin to determine the instrumentation calls to be filtered. Currently supported are absolute (filter all functions with a duration below a given threshold) and relative (filter all functions with a duration below the mean duration of all functions minus a given threshold).

• SCOREP_SUBSTRATE_DYNAMIC_FILTERING_THRESHOLD (integer, default 100000)

  Specifies the threshold to be used by the metrics in Score-P ticks (depends on SCOREP_TIMER) See SCOREP_SUBSTRATE_DYNAMIC_FILTERING_METHOD for details.

• SCOREP_SUBSTRATE_DYNAMIC_FILTERING_CONTINUE_DESPITE_FAILURE

  If set to true, True, TRUE, or 1 the plugin will continue to work even though it detected, that the program has been compiled with optimizations that make re-writing impossible (see Known issues).

• SCOREP_SUBSTRATE_DYNAMIC_FILTERING_CREATE_REPORT

  If set to true, True, TRUE, or 1 the plugin will write a report to stderr when finished

• SCOREP_SUBSTRATE_DYNAMIC_FILTERING_CREATE_FILTER_FILE

  If set to true, True, TRUE, or 1 the plugin will write a filter file to the experiment directory

Known issues

The compiler optimization -foptimize-sibling-calls is usually enabled for icc/gcc at -O2 and -O3. This will be detected by the plugin but the calls cannot be patched in this case. If you want to avoid this, but still use the other optimizations, just pass -fnooptimize-sibling-calls to your compiler.

The plugin only works when there is exactly one enter and one exit function for every instrumented function. This will probably not be the case with C++ programs.

If anything fails

1. Check whether the plugin library can be loaded from the LD_LIBRARY_PATH

2. Check whether you provide sane values for the environment variables.

3. Open an issue on Github.

License

For information regarding the license of this plugin, see LICENSE, for the license of uthash see uthash.LICENSE.

Author

• Philipp Trommler (https://github.com/Ferruck)
• Robert Schoene (robert dot schoene at tu-dresden dot de)