[PATCH v3 01/12] sched: fix imbalance flag reset
From: Rik van Riel <hidden>
Date: 2014-07-09 03:06:37
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 06/30/2014 12:05 PM, Vincent Guittot wrote:
The imbalance flag can stay set whereas there is no imbalance. Let assume that we have 3 tasks that run on a dual cores /dual cluster system. We will have some idle load balance which are triggered during tick. Unfortunately, the tick is also used to queue background work so we can reach the situation where short work has been queued on a CPU which already runs a task. The load balance will detect this imbalance (2 tasks on 1 CPU and an idle CPU) and will try to pull the waiting task on the idle CPU. The waiting task is a worker thread that is pinned on a CPU so an imbalance due to pinned task is detected and the imbalance flag is set. Then, we will not be able to clear the flag because we have at most 1 task on each CPU but the imbalance flag will trig to useless active load balance between the idle CPU and the busy CPU. We need to reset of the imbalance flag as soon as we have reached a balanced state. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Rik van Riel <redacted> - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJTvLFvAAoJEM553pKExN6DUcYIAJkj0fl4DIpx/7ywqSSCo4Da 1IpJI5Hz2zb+NunG8M/4kugDSYvMmiuNhFgG1ET7me11jxTcTqg0e8UZ4zJbW55u i14IVyXLW+AVhJNQc1Umu3c6tTnjawOIzLa4wJ5JCVFVTj/5AhHyJjbKfQJnew1q XlYm8+FPGmXQgJ0G3itmpx3gAYsrQIQXtIhM9wwgmKiysF4s+HZZppyZKtGbOtm4 ia408LsmjOYYp4vGSTa4F4IWx1K0fJVpz33TsCLb2pwKy6t/4hKf9tOn/wXPSLVc NbWrP7zYYJ8EaXgo/RV9OJnPXq0h0Tbp9eMtd4u/hRCrcHw1dUZBpDMIRkS5NzI= =uoh0 -----END PGP SIGNATURE-----