From: preeti@linux.vnet.ibm.com (Preeti U Murthy)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 01/11] sched: fix imbalance flag reset
Date: Sun, 25 May 2014 16:03:50 +0530 [thread overview]
Message-ID: <5381C70E.3030605@linux.vnet.ibm.com> (raw)
In-Reply-To: <1400860385-14555-2-git-send-email-vincent.guittot@linaro.org>
Hi Vincent,
On 05/23/2014 09:22 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.
Why do we do active balancing today when there is at-most 1 task on the
busiest cpu? Shouldn't we be skipping load balancing altogether? If we
do active balancing when the number of tasks = 1, it will lead to a ping
pong right?
Regards
Preeti U Murthy
next prev parent reply other threads:[~2014-05-25 10:33 UTC|newest]
Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-23 15:52 [PATCH v2 00/11] sched: consolidation of cpu_power Vincent Guittot
2014-05-23 15:52 ` [PATCH v2 01/11] sched: fix imbalance flag reset Vincent Guittot
2014-05-25 10:33 ` Preeti U Murthy [this message]
2014-05-26 7:49 ` Vincent Guittot
2014-05-26 9:16 ` Preeti U Murthy
2014-05-26 10:14 ` Vincent Guittot
2014-05-23 15:52 ` [PATCH v2 02/11] sched: remove a wake_affine condition Vincent Guittot
2014-05-27 12:48 ` Peter Zijlstra
2014-05-27 15:19 ` Vincent Guittot
2014-05-27 15:39 ` Peter Zijlstra
2014-05-27 16:14 ` Vincent Guittot
2014-05-28 6:49 ` Vincent Guittot
2014-05-28 15:09 ` Dietmar Eggemann
2014-05-28 15:25 ` Vincent Guittot
2014-05-27 13:43 ` Peter Zijlstra
2014-05-27 13:45 ` Peter Zijlstra
2014-05-27 15:20 ` Vincent Guittot
2014-05-23 15:52 ` [PATCH v2 03/11] sched: fix avg_load computation Vincent Guittot
2014-05-27 13:48 ` Peter Zijlstra
2014-05-23 15:52 ` [PATCH v2 04/11] sched: Allow all archs to set the power_orig Vincent Guittot
2014-05-30 14:04 ` Dietmar Eggemann
2014-05-30 14:46 ` Peter Zijlstra
2014-05-30 20:50 ` Vincent Guittot
2014-06-04 9:42 ` Dietmar Eggemann
2014-06-04 11:15 ` Vincent Guittot
2014-06-05 8:59 ` Dietmar Eggemann
2014-06-16 9:01 ` Vincent Guittot
2014-06-03 13:22 ` Morten Rasmussen
2014-06-03 14:02 ` Vincent Guittot
2014-06-04 11:17 ` Morten Rasmussen
2014-06-06 7:01 ` Vincent Guittot
2014-05-23 15:52 ` [PATCH v2 05/11] ARM: topology: use new cpu_power interface Vincent Guittot
2014-05-25 13:22 ` Preeti U Murthy
2014-05-26 8:25 ` Vincent Guittot
2014-05-26 9:19 ` Preeti U Murthy
2014-05-23 15:53 ` [PATCH v2 06/11] sched: add per rq cpu_power_orig Vincent Guittot
2014-05-23 15:53 ` [PATCH v2 07/11] Revert "sched: Put rq's sched_avg under CONFIG_FAIR_GROUP_SCHED" Vincent Guittot
2014-05-23 15:53 ` [PATCH v2 08/11] sched: get CPU's activity statistic Vincent Guittot
2014-05-27 17:32 ` Peter Zijlstra
2014-05-28 7:01 ` Vincent Guittot
2014-05-28 12:10 ` Morten Rasmussen
2014-05-28 13:15 ` Vincent Guittot
2014-05-28 15:47 ` Morten Rasmussen
2014-05-28 16:39 ` Vincent Guittot
2014-06-03 12:03 ` Morten Rasmussen
2014-06-03 15:59 ` Peter Zijlstra
2014-06-03 17:41 ` Morten Rasmussen
2014-06-03 15:50 ` Peter Zijlstra
2014-06-03 17:20 ` Morten Rasmussen
2014-06-04 7:47 ` Vincent Guittot
2014-06-04 8:08 ` Peter Zijlstra
2014-06-04 8:55 ` Morten Rasmussen
2014-06-04 9:23 ` Peter Zijlstra
2014-06-04 9:35 ` Vincent Guittot
2014-06-04 10:25 ` Morten Rasmussen
2014-06-04 9:44 ` Morten Rasmussen
2014-06-04 9:32 ` Vincent Guittot
2014-06-04 10:00 ` Morten Rasmussen
2014-06-04 10:17 ` Peter Zijlstra
2014-06-04 10:36 ` Morten Rasmussen
2014-06-04 10:55 ` Peter Zijlstra
2014-06-04 11:07 ` Vincent Guittot
2014-06-04 11:23 ` Morten Rasmussen
2014-06-04 11:52 ` Vincent Guittot
2014-06-04 13:09 ` Morten Rasmussen
2014-06-04 13:23 ` Morten Rasmussen
2014-05-28 15:17 ` Peter Zijlstra
2014-06-03 15:40 ` Peter Zijlstra
2014-06-03 17:16 ` Morten Rasmussen
2014-06-03 17:37 ` Peter Zijlstra
2014-06-03 17:39 ` Peter Zijlstra
2014-06-03 23:11 ` Yuyang Du
2014-05-30 9:50 ` Dietmar Eggemann
2014-05-30 19:20 ` Vincent Guittot
2014-06-01 11:33 ` Dietmar Eggemann
2014-06-02 14:07 ` Vincent Guittot
2014-05-23 15:53 ` [PATCH v2 09/11] sched: test the cpu's capacity in wake affine Vincent Guittot
2014-05-28 10:58 ` Peter Zijlstra
2014-05-28 11:15 ` Vincent Guittot
2014-11-24 0:34 ` Wanpeng Li
2014-11-24 13:23 ` Vincent Guittot
2014-05-23 15:53 ` [PATCH v2 10/11] sched: move cfs task on a CPU with higher capacity Vincent Guittot
2014-05-29 9:50 ` Peter Zijlstra
2014-05-29 19:37 ` Vincent Guittot
2014-05-30 6:29 ` Peter Zijlstra
2014-05-30 20:05 ` Vincent Guittot
2014-06-02 17:06 ` Vincent Guittot
2014-06-03 11:15 ` Peter Zijlstra
2014-06-03 12:31 ` Vincent Guittot
2014-05-29 14:04 ` Peter Zijlstra
2014-05-29 19:44 ` Vincent Guittot
2014-05-30 13:26 ` Dietmar Eggemann
2014-05-30 19:24 ` Vincent Guittot
2014-05-30 19:45 ` Nicolas Pitre
2014-05-30 20:07 ` Vincent Guittot
2014-05-23 15:53 ` [PATCH v2 11/11] sched: replace capacity by activity Vincent Guittot
2014-05-29 13:55 ` Peter Zijlstra
2014-05-29 19:51 ` Vincent Guittot
2014-06-02 6:21 ` Preeti U Murthy
2014-06-03 9:50 ` Vincent Guittot
2014-05-29 14:02 ` Peter Zijlstra
2014-05-29 19:56 ` Vincent Guittot
2014-05-30 6:34 ` Peter Zijlstra
2014-05-30 19:13 ` Vincent Guittot
2014-05-26 9:44 ` [PATCH v2 00/11] sched: consolidation of cpu_power Preeti U Murthy
2014-05-26 10:04 ` Vincent Guittot
2014-05-26 15:54 ` Vincent Guittot
2014-05-27 5:47 ` Preeti U Murthy
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