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[RFC PATCH 4/4] mm: kvmalloc support __GFP_RETRY_MAYFAIL for all sizes

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From: Michal Hocko <mhocko@suse.com>

Now that __GFP_RETRY_MAYFAIL has a reasonable semantic regardless of the
request size we can drop the hackish implementation for !costly orders.
__GFP_RETRY_MAYFAIL retries as long as the reclaim makes a forward
progress and backs of when we are out of memory for the requested size.
Therefore we do not need to enforce__GFP_NORETRY for !costly orders just
to silent the oom killer anymore.

Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 mm/util.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/mm/util.c b/mm/util.c
index 885a78d1941b..359d80333301 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -339,9 +339,9 @@ EXPORT_SYMBOL(vm_mmap);
  * Uses kmalloc to get the memory but if the allocation fails then falls back
  * to the vmalloc allocator. Use kvfree for freeing the memory.
  *
- * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported. __GFP_RETRY_MAYFAIL
- * is supported only for large (>32kB) allocations, and it should be used only if
- * kmalloc is preferable to the vmalloc fallback, due to visible performance drawbacks.
+ * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported.
+ * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
+ * preferable to the vmalloc fallback, due to visible performance drawbacks.
  *
  * Any use of gfp flags outside of GFP_KERNEL should be consulted with mm people.
  */
@@ -363,13 +363,7 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
 	if (size > PAGE_SIZE) {
 		kmalloc_flags |= __GFP_NOWARN;
 
-		/*
-		 * We have to override __GFP_RETRY_MAYFAIL by __GFP_NORETRY for !costly
-		 * requests because there is no other way to tell the allocator
-		 * that we want to fail rather than retry endlessly.
-		 */
-		if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL) ||
-				(size <= PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
+		if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
 			kmalloc_flags |= __GFP_NORETRY;
 	}
 
-- 
2.11.0

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[RFC PATCH 4/4] mm: kvmalloc support __GFP_RETRY_MAYFAIL for all sizes Michal Hocko <mhocko@kernel.org> - 2017-03-07 17:00 +0100

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