On 05/17/2017 01:09 AM, Michal Hocko wrote:
From: Michal Hocko <mhocko@xxxxxxxx>
While converting drm_[cm]alloc* helpers to kvmalloc* variants Chris
Wilson has wondered why we want to try kmalloc before vmalloc fallback
even for larger allocations requests. Let's clarify that one larger
physically contiguous block is less likely to fragment memory than many
scattered pages which can prevent more large blocks from being created.
Suggested-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
mm/util.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/mm/util.c b/mm/util.c
index 464df3489903..87499f8119f2 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -357,7 +357,10 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
WARN_ON_ONCE((flags & GFP_KERNEL) != GFP_KERNEL);
/*
- * Make sure that larger requests are not too disruptive - no OOM
+ * We want to attempt a large physically contiguous block first because
+ * it is less likely to fragment multiple larger blocks and therefore
+ * contribute to a long term fragmentation less than vmalloc fallback.
+ * However make sure that larger requests are not too disruptive - no OOM
* killer and no allocation failure warnings as we have a fallback
*/
Thanks for adding this, it's great to have. Here's a slightly polished version of your words, if you
like:
/*
* We want to attempt a large physically contiguous block first because
* it is less likely to fragment multiple larger blocks. This approach
* therefore contributes less to long term fragmentation than a vmalloc
* fallback would. However, make sure that larger requests are not too
* disruptive: no OOM killer and no allocation failure warnings, as we
* have a fallback.
*/
thanks,
john h
if (size > PAGE_SIZE) {
--
2.11.0
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
