mm: page_alloc: revert NUMA aspect of fair allocation policy
Commit 81c0a2bb ("mm: page_alloc: fair zone allocator policy") meant to bring aging fairness among zones in system, but it was overzealous and badly regressed basic workloads on NUMA systems. Due to the way kswapd and page allocator interacts, we still want to make sure that all zones in any given node are used equally for all allocations to maximize memory utilization and prevent thrashing on the highest zone in the node. While the same principle applies to NUMA nodes - memory utilization is obviously improved by spreading allocations throughout all nodes - remote references can be costly and so many workloads prefer locality over memory utilization. The original change assumed that zone_reclaim_mode would be a good enough predictor for that, but it turned out to be as indicative as a coin flip. Revert the NUMA aspect of the fairness until we can find a proper way to make it configurable and agree on a sane default. Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org> Reviewed-by: NMichal Hocko <mhocko@suse.cz> Signed-off-by: NMel Gorman <mgorman@suse.de> Cc: <stable@kernel.org> # 3.12 Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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