-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 07/08/2014 11:05 PM, Rik van Riel wrote: > 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>
Never mind that, Preeti explained the failure mode in more detail on irc, and I am no longer convinced this change is a good idea. - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJTvLi6AAoJEM553pKExN6DEAUH/A+dwZ4MYW1JafoKN3iaFzgr FqUzDayZ5NO2fSKNoa35CqvPhyZzAjeQn4H2yh0u/EhNI+1MzIqMY4i8l6dmB3QO woOj8pf6O5lB1+iWk9F2moEJRX2y3X8mhhysO3ujR8211Ic7t12Z195+SH7qD2OD xDjmRd/hTyNtn8mHOpcC2A69jaac8ZHKL6zNJcE9ax0IQxLTxZ+BzQnJhCtILEbD a2eYe/Dm039bvgZjIRmy0ht+GkTtUuA6Yn7/SxLbQMQ0eSolan0DC3M7TSB3SkDB z6lczf4lrMbyJdPhq1MX+C9YfbUAsICE2XQZYhpn/nopem0MTKBfQoLG4W3fWOg= =6eQR -----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/
