Add a comment and extend the doc.

diff --git a/doc/doxygen/options.doc b/doc/doxygen/options.doc
index 4c5af4b..d5a8f54 100644 (file)
--- a/doc/doxygen/options.doc
+++ b/doc/doxygen/options.doc
@@ -1141,6 +1141,8 @@ at least one huge page:
     sudo sh -c 'echo 1 > /proc/sys/vm/nr_hugepages'
 \endcode
 
     sudo sh -c 'echo 1 > /proc/sys/vm/nr_hugepages'
 \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.
 
 Then, you can pass the option --cfg=smpi/shared-malloc-hugepage:/home/huge
 to smpirun.
 

diff --git a/src/smpi/smpi_shared.cpp b/src/smpi/smpi_shared.cpp
index 38883ba..c72dad5 100644 (file)
--- a/src/smpi/smpi_shared.cpp
+++ b/src/smpi/smpi_shared.cpp
@@ -257,7 +257,12 @@ void* smpi_shared_malloc_partial(size_t size, size_t* shared_block_offsets, int
   XBT_DEBUG("global shared allocation. Blocksize %lu", smpi_shared_malloc_blocksize);
   /* Create a fd to a new file on disk, make it smpi_shared_malloc_blocksize big, and unlink it.
    * It still exists in memory but not in the file system (thus it cannot be leaked). */
   XBT_DEBUG("global shared allocation. Blocksize %lu", smpi_shared_malloc_blocksize);
   /* Create a fd to a new file on disk, make it smpi_shared_malloc_blocksize big, and unlink it.
    * It still exists in memory but not in the file system (thus it cannot be leaked). */

-  /* Create bogus file if not done already */
+  /* Create bogus file if not done already
+   * We need two different bogusfiles:
+   *    smpi_shared_malloc_bogusfile_huge_page is used for calls to mmap *with* MAP_HUGETLB,
+   *    smpi_shared_malloc_bogusfile is used for calls to mmap *without* MAP_HUGETLB.
+   * We cannot use a same file for the two type of calls, since the first one needs to be
+   * opened in a hugetlbfs mount point whereas the second needs to be a "classical" file. */

   if(use_huge_page && smpi_shared_malloc_bogusfile_huge_page == -1) {
     const char *const array[] = {huge_page_mount_point, "simgrid-shmalloc-XXXXXX", nullptr};
     char *huge_page_filename = xbt_str_join_array(array, "/");
   if(use_huge_page && smpi_shared_malloc_bogusfile_huge_page == -1) {
     const char *const array[] = {huge_page_mount_point, "simgrid-shmalloc-XXXXXX", nullptr};
     char *huge_page_filename = xbt_str_join_array(array, "/");