-----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.guit...@linaro.org>
Acked-by: Rik van Riel <r...@redhat.com> - -- 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----- -- 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/