Re: [PATCH] mm: don't invoke __alloc_pages_direct_compact when order 0

[David Rientjes <rientjes@google.com>]

On Mon, 9 Jul 2012, JoonSoo Kim wrote:

> I think __alloc_pages_direct_compact() can't be inlined by gcc,
> because it is so big and is invoked two times in __alloc_pages_nodemask().
> 

We could fix that by doing

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2057,7 +2057,7 @@ out:
 
 #ifdef CONFIG_COMPACTION
 /* Try memory compaction for high-order allocations before reclaim */
-static struct page *
+static __always_inline struct page *
 __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
 	struct zonelist *zonelist, enum zone_type high_zoneidx,
 	nodemask_t *nodemask, int alloc_flags, struct zone *preferred_zone,

but I'm not convinced that it's helpful for performance in the slowpath 
and there's no guarantee that it's called more often for order-0 
allocations since it is called as a fallback when should_alloc_retry() 
fails.

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