From 6b9a7460b6baf6c77fc3d23d927ddfc3f3f05bf3 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Mon, 7 Oct 2013 11:29:11 +0100 Subject: sched/numa: Retry migration of tasks to CPU on a preferred node When a preferred node is selected for a tasks there is an attempt to migrate the task to a CPU there. This may fail in which case the task will only migrate if the active load balancer takes action. This may never happen if the conditions are not right. This patch will check at NUMA hinting fault time if another attempt should be made to migrate the task. It will only make an attempt once every five seconds. Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel Cc: Andrea Arcangeli Cc: Johannes Weiner Cc: Srikar Dronamraju Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1381141781-10992-34-git-send-email-mgorman@suse.de Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 30 +++++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-) (limited to 'kernel/sched') diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 51a76008119..f84ac3fb581 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1011,6 +1011,23 @@ migrate: return migrate_task_to(p, env.best_cpu); } +/* Attempt to migrate a task to a CPU on the preferred node. */ +static void numa_migrate_preferred(struct task_struct *p) +{ + /* Success if task is already running on preferred CPU */ + p->numa_migrate_retry = 0; + if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid) + return; + + /* This task has no NUMA fault statistics yet */ + if (unlikely(p->numa_preferred_nid == -1)) + return; + + /* Otherwise, try migrate to a CPU on the preferred node */ + if (task_numa_migrate(p) != 0) + p->numa_migrate_retry = jiffies + HZ*5; +} + static void task_numa_placement(struct task_struct *p) { int seq, nid, max_nid = -1; @@ -1045,17 +1062,12 @@ static void task_numa_placement(struct task_struct *p) } } - /* - * Record the preferred node as the node with the most faults, - * requeue the task to be running on the idlest CPU on the - * preferred node and reset the scanning rate to recheck - * the working set placement. - */ + /* Preferred node as the node with the most faults */ if (max_faults && max_nid != p->numa_preferred_nid) { /* Update the preferred nid and migrate task if possible */ p->numa_preferred_nid = max_nid; p->numa_migrate_seq = 1; - task_numa_migrate(p); + numa_migrate_preferred(p); } } @@ -1111,6 +1123,10 @@ void task_numa_fault(int last_nidpid, int node, int pages, bool migrated) task_numa_placement(p); + /* Retry task to preferred node migration if it previously failed */ + if (p->numa_migrate_retry && time_after(jiffies, p->numa_migrate_retry)) + numa_migrate_preferred(p); + p->numa_faults_buffer[task_faults_idx(node, priv)] += pages; } -- cgit v1.2.3-18-g5258