Developer Guide

Contents

Using High-bandwidth Memory with
oneMKL

To achieve maximum performance,
Intel® oneAPI Math Kernel Library
may use the memkind library (https://github.com/memkind/memkind), which enables controlling memory characteristics and partitioning the heap between different kinds of memory. By default
Intel® oneAPI Math Kernel Library
memory manager tries to allocate memory to Multi-Channel Dynamic Random Access Memory (MCDRAM) using the memkind library on the 2
nd
generation Intel® Xeon Phi™ product family (for more details of MCDRAM, see https://software.intel.com/content/www/us/en/develop/articles/mcdram-high-bandwidth-memory-on-knights-landing-analysis-methods-tools.html). If allocation of memory to MCDRAM is not possible at the moment,
Intel® oneAPI Math Kernel Library
memory manager falls back to a regular system allocator.
By default the amount of MCDRAM available for
Intel® oneAPI Math Kernel Library
is unlimited. To control the amount of MCDRAM available for
Intel® oneAPI Math Kernel Library
, do either of the following:
  • Call
    mkl_set_memory_limit (MKL_MEM_MCDRAM,
    <limit_in_mbytes>
    )
  • Set the environment variable:
    • For the bash shell:
      MKL_FAST_MEMORY_LIMIT="
      <limit_in_mbytes>
      "
    • For a C shell (csh or tcsh):
      setenv MKL_FAST_MEMORY_LIMIT "
      <limit_in_mbytes>
      "
The setting of the limit affects all
Intel® oneAPI Math Kernel Library
functions, including user-callable memory functions such as
mkl_malloc
. Therefore, if an application calls
mkl_malloc
,
mkl_calloc
, or
mkl_realloc
, which always tries to allocate memory to MCDRAM, make sure that the limit is sufficient.
If you replace
Intel® oneAPI Math Kernel Library
memory management functions with your own functions (for details, see Redefining Memory Functions),
Intel® oneAPI Math Kernel Library
uses your functions and does not work with the memkind library directly.
Product and Performance Information
Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.
Notice revision #20201201

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.