[PATCH -mm 1/3] sched,numa: add cond_resched to task_numa_work

[riel]

From: Rik van Riel <riel@xxxxxxxxxx>

Normally task_numa_work scans over a fairly small amount of memory,
but it is possible to run into a large unpopulated part of virtual
memory, with no pages mapped. In that case, task_numa_work can run
for a while, and it may make sense to reschedule as required.

Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Reported-by: Xing Gang <gang.xing@xxxxxx>
Tested-by: Chegu Vinod <chegu_vinod@xxxxxx>
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 966cc2b..7815709 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1757,6 +1757,8 @@ void task_numa_work(struct callback_head *work)
 			start = end;
 			if (pages <= 0)
 				goto out;
+
+			cond_resched();
 		} while (end != vma->vm_end);
 	}
 
-- 
1.8.5.3

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