Commit-ID: a22b4b012340b988dbe7a58461d6fcc582f34aa0 Gitweb: http://git.kernel.org/tip/a22b4b012340b988dbe7a58461d6fcc582f34aa0 Author: Rik van Riel <riel@xxxxxxxxxx> AuthorDate: Mon, 23 Jun 2014 11:41:35 -0400 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Sat, 5 Jul 2014 11:17:40 +0200 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@xxxxxxxxxx> Cc: mgorman@xxxxxxx Cc: chegu_vinod@xxxxxx Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/1403538095-31256-8-git-send-email-riel@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- 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 7bb2f46..a140c6a 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 -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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