Modify pages_map() to support mapping uncommitted virtual memory.

If the OS overcommits:
- Commit all mappings in pages_map() regardless of whether the caller
  requested committed memory.
- Linux-specific: Specify MAP_NORESERVE to avoid
  unfortunate interactions with heuristic overcommit mode during
  fork(2).

This resolves #193.

1 files changed, 3 insertions, 7 deletions

diff --git a/src/chunk_mmap.c b/src/chunk_mmap.c
index e2e66bc9..f95ae756 100644
--- a/src/chunk_mmap.c
+++ b/src/chunk_mmap.c
@@ -16,18 +16,16 @@ chunk_alloc_mmap_slow(size_t size, size_t alignment, bool *zero, bool *commit)
 	do {
 		void *pages;
 		size_t leadsize;
-		pages = pages_map(NULL, alloc_size);
+		pages = pages_map(NULL, alloc_size, commit);
 		if (pages == NULL)
 			return (NULL);
 		leadsize = ALIGNMENT_CEILING((uintptr_t)pages, alignment) -
 		    (uintptr_t)pages;
-		ret = pages_trim(pages, alloc_size, leadsize, size);
+		ret = pages_trim(pages, alloc_size, leadsize, size, commit);
 	} while (ret == NULL);
 
 	assert(ret != NULL);
 	*zero = true;
-	if (!*commit)
-		*commit = pages_decommit(ret, size);
 	return (ret);
 }
 
@@ -54,7 +52,7 @@ chunk_alloc_mmap(void *new_addr, size_t size, size_t alignment, bool *zero,
 	assert(alignment != 0);
 	assert((alignment & chunksize_mask) == 0);
 
-	ret = pages_map(new_addr, size);
+	ret = pages_map(new_addr, size, commit);
 	if (ret == NULL || ret == new_addr)
 		return (ret);
 	assert(new_addr == NULL);
@@ -66,8 +64,6 @@ chunk_alloc_mmap(void *new_addr, size_t size, size_t alignment, bool *zero,
 
 	assert(ret != NULL);
 	*zero = true;
-	if (!*commit)
-		*commit = pages_decommit(ret, size);
 	return (ret);
 }