+ XBT_DEBUG("Mapping %s at %p through %d", shmname, mem, fd);
+ } else {
+ mem = shm_map(data->second.fd, size, &*data);
+ data->second.count++;
+ }
+ XBT_DEBUG("Shared malloc %zu in %p (metadata at %p)", size, mem, &*data);
+ return mem;
+}
+
+// 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");
+ const bool use_huge_page = huge_page_mount_point[0] != '\0';
+ 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) // allign to a huge page
+ mem = (void*)(((intptr_t)allocated_ptr+smpi_shared_malloc_blocksize-1)&~(smpi_shared_malloc_blocksize-1));
+ 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 */
+ if (use_huge_page && smpi_shared_malloc_bogusfile_huge_page == -1) {
+ char *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);
+ }