Commit-ID: 25b3e5a3344e1f700c1efec5b6f0199f04707fb1 Gitweb: http://git.kernel.org/tip/25b3e5a3344e1f700c1efec5b6f0199f04707fb1 Author: Rik van Riel <r...@redhat.com> AuthorDate: Thu, 5 Nov 2015 15:56:22 -0500 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Mon, 9 Nov 2015 16:13:27 +0100
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 <jstan...@redhat.com> Signed-off-by: Rik van Riel <r...@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: mgor...@suse.de Link: http://lkml.kernel.org/r/1446756983-28173-2-git-send-email-r...@redhat.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 824aa9f..f04fda8 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
