From: Rik van Riel <[email protected]> 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 <[email protected]> Signed-off-by: Rik van Riel <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
