sched/numa: Change scan period code to match intent
Reading through the scan period code and comment, it appears the intent was to slow down NUMA scanning when a majority of accesses are on the local node, specifically a local:remote ratio of 3:1. However, the code actually tests local / (local + remote), and the actual cut-off point was around 30% local accesses, well before a task has actually converged on a node. Changing the threshold to 7 means scanning slows down when a task has around 70% of its accesses local, which appears to match the intent of the code more closely. Signed-off-by: Rik van Riel <riel@redhat.com> Cc: mgorman@suse.de Cc: chegu_vinod@hp.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1403538095-31256-8-git-send-email-riel@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -1452,12 +1452,12 @@ static void update_numa_active_node_mask(struct numa_group *numa_group)
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/*
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/*
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* When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
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* When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
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* increments. The more local the fault statistics are, the higher the scan
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* increments. The more local the fault statistics are, the higher the scan
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* period will be for the next scan window. If local/remote ratio is below
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* period will be for the next scan window. If local/(local+remote) ratio is
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* NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) the
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* below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
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* scan period will decrease
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* the scan period will decrease. Aim for 70% local accesses.
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*/
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*/
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#define NUMA_PERIOD_SLOTS 10
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#define NUMA_PERIOD_SLOTS 10
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#define NUMA_PERIOD_THRESHOLD 3
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#define NUMA_PERIOD_THRESHOLD 7
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/*
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/*
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* Increase the scan period (slow down scanning) if the majority of
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* Increase the scan period (slow down scanning) if the majority of
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