[PATCH] page-allocator: Always wake kswapd when restarting an allocation attempt after direct reclaim failed

[Mel Gorman]

If a direct reclaim makes no forward progress, it considers whether it should
go OOM or not. Whether OOM is triggered or not, it may retry the application
afterwards. In times past, this would always wake kswapd as well but
currently, kswapd is not woken up after direct reclaim fails. For
order-0 allocations, this makes little difference but if there is a heavy
mix of higher-order allocations that direct reclaim is failing for, it
might mean that kswapd is not reclaiming for higher orders as much as it
did previously.

This patch wakes up kswapd when an allocation is being retried after a direct
reclaim failure. It would be expected that kswapd is already awake, but
this has the effect of telling kswapd to reclaim at the higher order as well.

Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
--- 
 mm/page_alloc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index bf72055..dfa4362 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1817,9 +1817,9 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 	if (NUMA_BUILD && (gfp_mask & GFP_THISNODE) == GFP_THISNODE)
 		goto nopage;
 
+restart:
 	wake_all_kswapd(order, zonelist, high_zoneidx);
 
-restart:
 	/*
 	 * OK, we're below the kswapd watermark and have kicked background
 	 * reclaim. Now things get more complex, so set up alloc_flags according
--
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