Currently the caller of get_huge_pages() is expected to align the length to
the hugepage boundary. This requires the caller to know alignment is required,
have an ALIGN() macro and know which pagesize is in use. As well as being
a useless and unnecessary burden, it prevents anything useful being done
with the wasted bytes. This patch relieves the caller of some responsibility.
Signed-off-by: Mel Gorman <[EMAIL PROTECTED]>
---
alloc.c | 32 ++++++++++++++++++++------------
1 files changed, 20 insertions(+), 12 deletions(-)
diff --git a/alloc.c b/alloc.c
index 750b2cb..b87a60d 100644
--- a/alloc.c
+++ b/alloc.c
@@ -69,16 +69,17 @@ static void *fallback_base_pages(size_t len, ghp_t flags)
* flags: Flags specifying the behaviour of the function
*
* This function allocates a region of memory backed by huge pages and
- * at least hugepage-aligned. This is not a suitable drop-in for malloc()
- * and is only suitable in the event the length is expected to be
- * hugepage-aligned. However, a malloc-like library could use this function
- * to create additional heap similar in principal to what morecore does for
- * glibc malloc.
+ * at least hugepage-aligned. This is not a suitable drop-in for malloc().
+ * As the length is always aligned to a hugepage-boundary, on average
+ * half a hugepage will be wasted unless care is taken. The intention is that
+ * a malloc-like library uses this function to create additional heap similar
+ * in principal to what morecore does for glibc malloc.
*/
void *get_huge_pages(size_t len, ghp_t flags)
{
void *buf;
int heap_fd;
+ size_t aligned_len, wasteage;
/* Create a file descriptor for the new region */
heap_fd = hugetlbfs_unlinked_fd();
@@ -87,15 +88,22 @@ void *get_huge_pages(size_t len, ghp_t flags)
return NULL;
}
+ /* Align the len parameter */
+ aligned_len = ALIGN(len, gethugepagesize());
+ wasteage = aligned_len - len;
+ if (wasteage != 0)
+ DEBUG("get_huge_pages: Wasted %zd bytes due to alignment\n",
+ wasteage);
+
/* Map the requested region */
- buf = mmap(NULL, len, PROT_READ|PROT_WRITE,
- MAP_PRIVATE, heap_fd, 0);
+ buf = mmap(NULL, aligned_len, PROT_READ|PROT_WRITE,
+ MAP_PRIVATE, heap_fd, 0);
if (buf == MAP_FAILED) {
close(heap_fd);
/* Try falling back to base pages if allowed */
if (flags & GHP_FALLBACK)
- return fallback_base_pages(len, flags);
+ return fallback_base_pages(aligned_len, flags);
WARNING("get_huge_pages: New region mapping failed (flags:
0x%lX): %s\n",
flags, strerror(errno));
@@ -103,19 +111,19 @@ void *get_huge_pages(size_t len, ghp_t flags)
}
/* Fault the region to ensure accesses succeed */
- if (hugetlbfs_prefault(heap_fd, buf, len) != 0) {
- munmap(buf, len);
+ if (hugetlbfs_prefault(heap_fd, buf, aligned_len) != 0) {
+ munmap(buf, aligned_len);
close(heap_fd);
/* Try falling back to base pages if allowed */
if (flags & GHP_FALLBACK)
- return fallback_base_pages(len, flags);
+ return fallback_base_pages(aligned_len, flags);
}
/* Close the file so we do not have to track the descriptor */
if (close(heap_fd) != 0) {
WARNING("Failed to close new heap fd: %s\n", strerror(errno));
- munmap(buf, len);
+ munmap(buf, aligned_len);
return NULL;
}
--
1.5.6.5
-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Libhugetlbfs-devel mailing list
Libhugetlbfs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/libhugetlbfs-devel
