IOFlex

IOFlex is a portable I/O tuning tool designed to optimize I/O performance for HPC (High-Performance Computing) applications without requiring source code modifications.

IOFlex Consists of two main component (i) IOFlex I/O wrapper library and (ii) IOFlex I/O auto-tuning library.

I. IOFlex I/O Wrapper

IOFlex adjusts I/O configurations like Lustre striping and ROMIO hints. It integrates seamlessly, either through LD_PRELOAD or by linking the shared library during compilation. IOFlex Works with various MPI environments like OpenMPI and MPT, with support for profiling tools like Darshan. I/O configurations set using IOFlex override any previously I/O configuration.

Prerequisites

• libconfuse: https://github.com/libconfuse/libconfuse.git

Building and Installation

$ ./autogen.sh
# By default, ioflex is installed in `pwd` if not changed via --prefix
$ ./configure --with-libconfuse=<path to libconfuse> --prefix=<path to install dir>
$ make && make install

Setting IO Configurations

• config.conf file by default specifies the IO configs IOFlex should adapt.
• Supported IO configurations

striping_unit = ...
striping_factor = ...
romio_filesystem_type = ...
romio_ds_write = ...
romio_ds_read = ...
romio_cb_read = ...
romio_cb_write = ...
cb_nodes = ...
cb_buffer_size = ...
cb_config_list = ...

• Parameters absent from the configuration file are left unset, retaining the values previously set by the application or default values if none were specified.

Using IOFlex shared library

• Using LD_PRELOAD without changing source code:

export LD_PRELOAD=<path-to-libioflex>/libioflex.so
mpirun ...

• OR, by recompiling with shared library flags

-L$IOFLEX_LIB_PATH -lioflex -Wl,-rpath=$IOFLEX_LIB_PATH

Important Notes

• You can use Darshan I/O profiler with IOFlex. Just make sure to load IOFlex before Darshan
• IOFlex supports HDF5 and NetCDF I/O libraries.
• Compile and install IOFlex with the same environment (compiler and MPI) the program use
• Running with MPT:
  • Set the following flag export MPI_SHEPHERD=true
  • For MPT + OpenMP: LD_PRELOAD hangs so recompile with shared library flags
• Running with OpenMPI:
  • Use ROMIO MCA component mpirun -np $NP --mca io romio321 <exe>

II. IOFlex I/O Auto-tuning tool

Automated I/O tuning to identify optimal configurations for different workloads.