diff options
| author | Rik van Riel <[email protected]> | 2015-11-05 15:56:22 -0500 |
|---|---|---|
| committer | Ingo Molnar <[email protected]> | 2015-11-09 16:13:27 +0100 |
| commit | 25b3e5a3344e1f700c1efec5b6f0199f04707fb1 (patch) | |
| tree | 5f3b54f6f8f9a207fc717bda3902f47d83be91f0 | |
| parent | 66ef3493d4bb387f5a83915e33dc893102fd1b43 (diff) | |
sched/numa: Fix math underflow in task_tick_numa()
The NUMA balancing code implements delays in scanning by
advancing curr->node_stamp beyond curr->se.sum_exec_runtime.
With unsigned math, that creates an underflow, which results
in task_numa_work being queued all the time, even when we
don't want to.
Avoiding the math underflow makes it possible to reduce CPU
overhead in the NUMA balancing code.
Reported-and-tested-by: Jan Stancek <[email protected]>
Signed-off-by: Rik van Riel <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
| -rw-r--r-- | kernel/sched/fair.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 824aa9f501a3..f04fda8f669c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2302,7 +2302,7 @@ void task_tick_numa(struct rq *rq, struct task_struct *curr) now = curr->se.sum_exec_runtime; period = (u64)curr->numa_scan_period * NSEC_PER_MSEC; - if (now - curr->node_stamp > period) { + if (now > curr->node_stamp + period) { if (!curr->node_stamp) curr->numa_scan_period = task_scan_min(curr); curr->node_stamp += period; |