sched/numa: Stay on the same node if CLONE_VM

A newly spawned thread inside a process should stay on the same
NUMA node as its parent. This prevents processes from being "torn"
across multiple NUMA nodes every time they spawn a new thread.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-49-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 9 insertions, 5 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 51092d5cc64c..3e2c893df173 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1696,7 +1696,7 @@ int wake_up_state(struct task_struct *p, unsigned int state)
  *
  * __sched_fork() is basic setup used by init_idle() too:
  */
-static void __sched_fork(struct task_struct *p)
+static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
 {
         p->on_rq                        = 0;
 
@@ -1725,11 +1725,15 @@ static void __sched_fork(struct task_struct *p)
                 p->mm->numa_scan_seq = 0;
         }
 
+        if (clone_flags & CLONE_VM)
+                p->numa_preferred_nid = current->numa_preferred_nid;
+        else
+                p->numa_preferred_nid = -1;
+
         p->node_stamp = 0ULL;
         p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
         p->numa_migrate_seq = 1;
         p->numa_scan_period = sysctl_numa_balancing_scan_delay;
-        p->numa_preferred_nid = -1;
         p->numa_work.next = &p->numa_work;
         p->numa_faults = NULL;
         p->numa_faults_buffer = NULL;
@@ -1761,12 +1765,12 @@ void set_numabalancing_state(bool enabled)
 /*
  * fork()/clone()-time setup:
  */
-void sched_fork(struct task_struct *p)
+void sched_fork(unsigned long clone_flags, struct task_struct *p)
 {
         unsigned long flags;
         int cpu = get_cpu();
 
-        __sched_fork(p);
+        __sched_fork(clone_flags, p);
         /*
          * We mark the process as running here. This guarantees that
          * nobody will actually run it, and a signal or other external
@@ -4287,7 +4291,7 @@ void init_idle(struct task_struct *idle, int cpu)
 
         raw_spin_lock_irqsave(&rq->lock, flags);
 
-        __sched_fork(idle);
+        __sched_fork(0, idle);
         idle->state = TASK_RUNNING;
         idle->se.exec_start = sched_clock();