powerpc/numa: Set a smaller value for RECLAIM_DISTANCE to enable zone reclaim
I noticed /proc/sys/vm/zone_reclaim_mode was 0 on a ppc64 NUMA box. It gets enabled via this: /* * If another node is sufficiently far away then it is better * to reclaim pages in a zone before going off node. */ if (distance > RECLAIM_DISTANCE) zone_reclaim_mode = 1; Since we use the default value of 20 for REMOTE_DISTANCE and 20 for RECLAIM_DISTANCE it never kicks in. The local to remote bandwidth ratios can be quite large on System p machines so it makes sense for us to reclaim clean pagecache locally before going off node. The patch below sets a smaller value for RECLAIM_DISTANCE and thus enables zone reclaim. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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@ -18,6 +18,16 @@ struct device_node;
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*/
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#define RECLAIM_DISTANCE 10
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/*
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* Before going off node we want the VM to try and reclaim from the local
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* node. It does this if the remote distance is larger than RECLAIM_DISTANCE.
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* With the default REMOTE_DISTANCE of 20 and the default RECLAIM_DISTANCE of
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* 20, we never reclaim and go off node straight away.
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*
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* To fix this we choose a smaller value of RECLAIM_DISTANCE.
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*/
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#define RECLAIM_DISTANCE 10
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#include <asm/mmzone.h>
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static inline int cpu_to_node(int cpu)
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