+// Align functions, from http://stackoverflow.com/questions/4840410/how-to-align-a-pointer-in-c
+#define PAGE_SIZE 0x1000
+#define ALIGN_UP(n, align) (((n) + (align)-1) & -(align))
+#define ALIGN_DOWN(n, align) ((n) & -(align))
+
+#define HUGE_PAGE_SIZE 1<<21
+
+/*
+ * Similar to smpi_shared_malloc, but only sharing the blocks described by shared_block_offsets.
+ * This array contains the offsets (in bytes) of the block to share.
+ * Even indices are the start offsets (included), odd indices are the stop offsets (excluded).
+ * For instance, if shared_block_offsets == {27, 42}, then the elements mem[27], mem[28], ..., mem[41] are shared. The others are not.
+ */
+void* smpi_shared_malloc_partial(size_t size, size_t* shared_block_offsets, int nb_shared_blocks)
+{
+ char *huge_page_mount_point = xbt_cfg_get_string("smpi/shared-malloc-hugepage");
+ bool use_huge_page = huge_page_mount_point[0] != '\0';
+#ifndef MAP_HUGETLB /* If the system header don't define that mmap flag */
+ xbt_assert(not use_huge_page,
+ "Huge pages are not available on your system, you cannot use the smpi/shared-malloc-hugepage option.");
+ use_huge_page = 0;
+#endif
+ smpi_shared_malloc_blocksize = static_cast<unsigned long>(xbt_cfg_get_double("smpi/shared-malloc-blocksize"));
+ void *mem, *allocated_ptr;
+ size_t allocated_size;
+ if(use_huge_page) {
+ xbt_assert(smpi_shared_malloc_blocksize == HUGE_PAGE_SIZE, "the block size of shared malloc should be equal to the size of a huge page.");
+ allocated_size = size + 2*smpi_shared_malloc_blocksize;
+ }
+ else {
+ xbt_assert(smpi_shared_malloc_blocksize % PAGE_SIZE == 0, "the block size of shared malloc should be a multiple of the page size.");
+ allocated_size = size;
+ }
+
+
+ /* First reserve memory area */
+ allocated_ptr = mmap(NULL, allocated_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+
+
+ xbt_assert(allocated_ptr != MAP_FAILED, "Failed to allocate %zuMiB of memory. Run \"sysctl vm.overcommit_memory=1\" as root "
+ "to allow big allocations.\n",
+ size >> 20);
+ if(use_huge_page)
+ mem = (void*)ALIGN_UP((uint64_t)allocated_ptr, HUGE_PAGE_SIZE);
+ else
+ mem = allocated_ptr;
+
+ 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
+ * 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, "/");
+ smpi_shared_malloc_bogusfile_huge_page = mkstemp(huge_page_filename);
+ XBT_DEBUG("bogusfile_huge_page: %s\n", huge_page_filename);
+ unlink(huge_page_filename);
+ xbt_free(huge_page_filename);
+ }
+ if(smpi_shared_malloc_bogusfile == -1) {
+ char *name = xbt_strdup("/tmp/simgrid-shmalloc-XXXXXX");
+ smpi_shared_malloc_bogusfile = mkstemp(name);
+ XBT_DEBUG("bogusfile : %s\n", name);
+ unlink(name);
+ xbt_free(name);
+ char* dumb = (char*)calloc(1, smpi_shared_malloc_blocksize);
+ ssize_t err = write(smpi_shared_malloc_bogusfile, dumb, smpi_shared_malloc_blocksize);
+ if(err<0)
+ xbt_die("Could not write bogus file for shared malloc");
+ xbt_free(dumb);
+ }
+
+ int mmap_base_flag = MAP_FIXED | MAP_SHARED | MAP_POPULATE;
+ int mmap_flag = mmap_base_flag;
+ int huge_fd = use_huge_page ? smpi_shared_malloc_bogusfile_huge_page : smpi_shared_malloc_bogusfile;
+#ifdef MAP_HUGETLB
+ if(use_huge_page)
+ mmap_flag |= MAP_HUGETLB;
+#endif
+
+ XBT_DEBUG("global shared allocation, begin mmap");
+
+ /* Map the bogus file in place of the anonymous memory */
+ for(int i_block = 0; i_block < nb_shared_blocks; i_block ++) {
+ XBT_DEBUG("\tglobal shared allocation, mmap block %d/%d", i_block+1, nb_shared_blocks);
+ size_t start_offset = shared_block_offsets[2*i_block];
+ size_t stop_offset = shared_block_offsets[2*i_block+1];
+ xbt_assert(start_offset < stop_offset, "start_offset (%zu) should be lower than stop offset (%zu)", start_offset, stop_offset);
+ xbt_assert(stop_offset <= size, "stop_offset (%zu) should be lower than size (%zu)", stop_offset, size);
+ if(i_block < nb_shared_blocks-1)
+ xbt_assert(stop_offset < shared_block_offsets[2*i_block+2],
+ "stop_offset (%zu) should be lower than its successor start offset (%zu)", stop_offset, shared_block_offsets[2*i_block+2]);
+ size_t start_block_offset = ALIGN_UP(start_offset, smpi_shared_malloc_blocksize);
+ size_t stop_block_offset = ALIGN_DOWN(stop_offset, smpi_shared_malloc_blocksize);
+ for (unsigned block_id=0, i = start_block_offset / smpi_shared_malloc_blocksize; i < stop_block_offset / smpi_shared_malloc_blocksize; block_id++, i++) {
+ XBT_DEBUG("\t\tglobal shared allocation, mmap block offset %d", block_id);