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I try to analyse the scaling behaviour of a C++-program that I have parallelised with Intel OpenMP and the Intel Composer XE 2014. When I run a "Advanced Hotspot Analyses", I get as a result, that a library function called "kmp print storage map gtip" consumes the second longest part of the total runtime. I googled for the meaning of this routine, but I didn't get results. Is this routine related to the std::map datastructures, that I am using in this part of the algorithm? Thanks in advance!

EDIT Now I removed one barrier and could speedup everything. But now a new Hotspot comes into play. Suddenly When I do a Locks & Wait analysis I have at the first position "OMP Join Barrier mkl_blas_daxpy_omp:115" and "OMP Join Barrier mkl_blas_dcopy:155"". But I don't call any mkl routine explicitly. How can I investigate this further?

user3572032
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  • I forget to mention that it is contained in the OpenMP library. – user3572032 Nov 17 '14 at 13:27
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    How long does your test take, is it trivially short? – steabert Nov 17 '14 at 13:40
  • It was a testcase that needed 3.5 seconds. By using bigger data I get _kmp_barrier and _kmp_x86_pause at positions 2 and three. This looks much "better" i.e. more realistic. Thanks, I thought that a testcase with 3.5 seconds would be non-trivial enough. – user3572032 Nov 17 '14 at 13:55

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__kmp_print_storage_map_gtid gets called whenever the environment variable KMP_STORAGE_MAP is set to true or verbose. It prints to the standard error stream the location of various objects used by the OpenMP runtime library. As I/O operations are slow in general, it is not surprising that it takes a lot of your program's execution time, especially when it comes to short test cases.

Since KMP_STORAGE_MAP is undocumented and its default value is false, it is safe to assume that it is there only to be used in special cases by other tools, e.g. by VTune while doing hotspot analysis. When your program runs normally, the function won't get called at all.

Hristo Iliev
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You can trace the MKL call in your code looking at the stack panel on the right, when "mkl_blas_dcopy" hotspot is selected in Bottom-up - you should be able see call chain up to main(). Maybe some other library called from your code uses MKL. enter image description here

Kirill Rogozhin
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