From: Tim Chen <tim.c.chen@linux.intel.com>
To: Kirill Tkhai <ktkhai@parallels.com>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Mike Galbraith <umgwanakikbuti@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Nicolas Pitre <nicolas.pitre@linaro.org>,
Ingo Molnar <mingo@kernel.org>, Paul Turner <pjt@google.com>,
tkhai@yandex.ru
Subject: Re: [PATCH 4/5] sched/fair: Remove double_lock_balance() from active_load_balance_cpu_stop()
Date: Thu, 24 Jul 2014 17:04:11 -0700 [thread overview]
Message-ID: <1406246651.2970.841.camel@schen9-DESK> (raw)
In-Reply-To: <1406028628.3526.22.camel@tkhai>
On Tue, 2014-07-22 at 15:30 +0400, Kirill Tkhai wrote:
> Bad situation:
>
> double_lock_balance() drops busiest_rq lock. The busiest_rq is *busiest*,
> and a lot of tasks and context switches there. We are dropping the lock
> and waiting for it again.
>
> Let's just detach the task and once finally unlock it!
>
> Warning: this admits unlocked using of can_migrate_task(), throttled_lb_pair(),
> and task_hot(). I added comments about that.
>
Wonder if we should also consider removing double_lock_balance usage
from rt.c and deadline.c? Then those two schedulers will also not
lock both the source and destination queues at the same time
for load balancing.
Tim
next prev parent reply other threads:[~2014-07-25 0:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20140722102425.29682.24086.stgit@tkhai>
2014-07-22 11:30 ` [PATCH 1/5] sched: Wrapper for checking task_struct's .on_rq Kirill Tkhai
2014-07-22 11:30 ` [PATCH 2/5] sched: Teach scheduler to understand ONRQ_MIGRATING state Kirill Tkhai
2014-07-22 11:45 ` Peter Zijlstra
2014-07-22 12:24 ` Kirill Tkhai
2014-07-22 12:25 ` Steven Rostedt
2014-07-22 13:20 ` Kirill Tkhai
2014-07-24 19:03 ` Oleg Nesterov
2014-07-25 7:11 ` Kirill Tkhai
2014-07-22 11:30 ` [PATCH 3/5] sched: Remove double_rq_lock() from __migrate_task() Kirill Tkhai
2014-07-22 11:30 ` [PATCH 4/5] sched/fair: Remove double_lock_balance() from active_load_balance_cpu_stop() Kirill Tkhai
2014-07-25 0:04 ` Tim Chen [this message]
2014-07-25 7:05 ` Kirill Tkhai
2014-07-22 11:31 ` [PATCH 5/5] sched/fair: Remove double_lock_balance() from load_balance() Kirill Tkhai
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