area is mapped on a 1MiB file on disk. If the returned bloc is of size
N MiB, then the same file is mapped N times to cover the whole bloc.
At the end, no matter how many SMPI_SHARED_MALLOC you do, this will
-only consume 1 MiB in memory.
+only consume 1 MiB in memory.
You can disable this behavior and come back to regular mallocs (for
example for debugging purposes) using \c "no" as a value.
As an example,
-\code{.unparsed}
+\code{.C}
mem = SMPI_PARTIAL_SHARED_MALLOC(500, {27,42 , 100,200}, 2);
\endcode
Then, it can be deallocated by calling SMPI_SHARED_FREE(mem).
-When smpi/shared-malloc:global is used, it is possible to optimize even
-further the memory consumption and the simulation time by using huge pages.
-To do so, it is required to mount a hugetlbfs on your system and allocate
+When smpi/shared-malloc:global is used, the memory consumption problem
+is solved, but it may induce too much load on the kernel's pages table.
+In this case, you should use huge pages so that we create only one
+entry per Mb of malloced data instead of one entry per 4k.
+To activate this, you must mount a hugetlbfs on your system and allocate
at least one huge page:
-\code{.unparsed}
+\code{.sh}
mkdir /home/huge
sudo mount none /home/huge -t hugetlbfs -o rw,mode=0777
- sudo sh -c 'echo 1 > /proc/sys/vm/nr_hugepages'
+ sudo sh -c 'echo 1 > /proc/sys/vm/nr_hugepages' # echo more if you need more
\endcode
-Note that at least one huge page is required for smpirun, but you can set
-an higher number of huge pages in nr_hugepages (e.g. "echo 27").
Then, you can pass the option --cfg=smpi/shared-malloc-hugepage:/home/huge
-to smpirun.
+to smpirun to actually activate the huge page support in shared mallocs.
\subsection options_model_smpi_wtime smpi/wtime: Inject constant times for calls to MPI_Wtime
\section options_index Index of all existing configuration options
\note
- Almost all options are defined in <i>src/simgrid/sg_config.c</i>. You may
- want to check this file, too, but this index should be somewhat complete
- for the moment (May 2015).
-
-\note
- \b Please \b note: You can also pass the command-line option "--help" and
- "--help-cfg" to an executable that uses simgrid.
+ The full list can be retrieved by passing "--help" and
+ "--help-cfg" to an executable that uses SimGrid.
- \c clean-atexit: \ref options_generic_clean_atexit
- \c smpi/privatization: \ref options_smpi_privatization
- \c smpi/send-is-detached-thresh: \ref options_model_smpi_detached
- \c smpi/shared-malloc: \ref options_model_smpi_shared_malloc
+- \c smpi/shared-malloc-hugepage: \ref options_model_smpi_shared_malloc
- \c smpi/simulate-computation: \ref options_smpi_bench
- \c smpi/test: \ref options_model_smpi_test
- \c smpi/wtime: \ref options_model_smpi_wtime
