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mm: exclude memoryless nodes from zone_reclaim
We had a report about strange OOM killer strikes on a PPC machine although there was a lot of swap free and a tons of anonymous memory which could be swapped out. In the end it turned out that the OOM was a side effect of zone reclaim which wasn't unmapping and swapping out and so the system was pushed to the OOM. Although this sounds like a bug somewhere in the kswapd vs. zone reclaim vs. direct reclaim interaction numactl on the said hardware suggests that the zone reclaim should not have been set in the first place: node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 node 0 size: 0 MB node 0 free: 0 MB node 2 cpus: node 2 size: 7168 MB node 2 free: 6019 MB node distances: node 0 2 0: 10 40 2: 40 10 So all the CPUs are associated with Node0 which doesn't have any memory while Node2 contains all the available memory. Node distances cause an automatic zone_reclaim_mode enabling. Zone reclaim is intended to keep the allocations local but this doesn't make any sense on the memoryless nodes. So let's exclude such nodes for init_zone_allows_reclaim which evaluates zone reclaim behavior and suitable reclaim_nodes. Signed-off-by: Michal Hocko <mhocko@suse.cz> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com> Tested-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com> Acked-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1870,7 +1870,7 @@ static void __paginginit init_zone_allows_reclaim(int nid)
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{
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int i;
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for_each_online_node(i)
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for_each_node_state(i, N_MEMORY)
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if (node_distance(nid, i) <= RECLAIM_DISTANCE)
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node_set(i, NODE_DATA(nid)->reclaim_nodes);
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else
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@ -4919,7 +4919,8 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
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pgdat->node_id = nid;
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pgdat->node_start_pfn = node_start_pfn;
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init_zone_allows_reclaim(nid);
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if (node_state(nid, N_MEMORY))
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init_zone_allows_reclaim(nid);
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#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
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get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
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#endif
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