Messages in this thread Patch in this message | | | From | riel@redhat ... | Subject | [PATCH 7/7] sched,numa: change scan period code to match intent | Date | Mon, 23 Jun 2014 11:41:35 -0400 |
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From: Rik van Riel <riel@redhat.com>
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.
Cc: Mel Gorman <mgorman@suse.de> Signed-off-by: Rik van Riel <riel@redhat.com> --- kernel/sched/fair.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index ee35576..1aaa3b4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1452,12 +1452,12 @@ static void update_numa_active_node_mask(struct numa_group *numa_group) /* * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS * increments. The more local the fault statistics are, the higher the scan - * period will be for the next scan window. If local/remote ratio is below - * NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) the - * scan period will decrease + * period will be for the next scan window. If local/(local+remote) ratio is + * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) + * the scan period will decrease. Aim for 70% local accesses. */ #define NUMA_PERIOD_SLOTS 10 -#define NUMA_PERIOD_THRESHOLD 3 +#define NUMA_PERIOD_THRESHOLD 7 /* * Increase the scan period (slow down scanning) if the majority of -- 1.8.5.3
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