[PATCH -next] sched/numa: document CLONE_VM behavior

[Davidlohr Bueso]

From: Davidlohr Bueso <davidlohr@xxxxxx>

The changelog for Rik's "sched/numa: Stay on the same node if CLONE_VM" patch
serves well documented in the code.

Signed-off-by: Davidlohr Bueso <davidlohr@xxxxxx>
---
 kernel/sched/core.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7f45fd5..a2d690c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1743,10 +1743,16 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
 
 #ifdef CONFIG_NUMA_BALANCING
 	if (p->mm && atomic_read(&p->mm->mm_users) == 1) {
-		p->mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
 		p->mm->numa_scan_seq = 0;
+		p->mm->numa_next_scan = jiffies +
+			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
 	}
 
+	/*
+	 * A newly spawned thread 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.
+	 */
 	if (clone_flags & CLONE_VM)
 		p->numa_preferred_nid = current->numa_preferred_nid;
 	else
-- 
1.8.1.4



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/