[PATCH] mm: slub: Do not wake kswapd for SLUBs speculative high-order allocations

[Mel Gorman]

To avoid locking and per-cpu overhead, SLUB optimisically uses
high-order allocations and falls back to lower allocations if they fail.
However, by simply trying to allocate, kswapd is woken up to start
reclaiming at that order. On a desktop system, two users report that the
system is getting locked up with kswapd using large amounts of CPU.
Using SLAB instead of SLUB makes this problem go away.

This patch prevents kswapd being woken up for high-order allocations.

Not-signed-off-yet: Mel Gorman <mgorman@xxxxxxx>
---
 mm/slub.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 9d2e5e4..98c358d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1170,7 +1170,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	 * Let the initial higher-order allocation fail under memory pressure
 	 * so we fall-back to the minimum order allocation.
 	 */
-	alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL;
+	alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY | __GFP_NO_KSWAPD) & ~__GFP_NOFAIL;
 
 	page = alloc_slab_page(alloc_gfp, node, oo);
 	if (unlikely(!page)) {

--vkogqOf2sHV7VnPd
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Content-Disposition: attachment; filename="mm-slub-do-not-take-expensive-steps-for-slub-high-orders.patch"