lkml.org 
[lkml]   [2014]   [Jul]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 01/12] sched: fix imbalance flag reset
-----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 <riel@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-----


\
 
 \ /
  Last update: 2014-07-09 06:01    [W:0.368 / U:0.364 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site