From: Ingo Molnar <mingo@elte.hu>
To: John Hawkes <hawkes@oss.sgi.com>
Cc: nickpiggin@yahoo.com.au, akpm@osdl.org,
linux-kernel@vger.kernel.org, jbarnes@sgi.com, hawkes@sgi.com
Subject: Re: [PATCH, 2.6.9] improved load_balance() tolerance for pinned tasks
Date: Wed, 20 Oct 2004 21:59:30 +0200 [thread overview]
Message-ID: <20041020195930.GA29735@elte.hu> (raw)
In-Reply-To: <200410201936.i9KJa4FF026174@oss.sgi.com>
* John Hawkes <hawkes@oss.sgi.com> wrote:
> A large number of processes that are pinned to a single CPU results in
> every other CPU's load_balance() seeing this overloaded CPU as "busiest",
> yet move_tasks() never finds a task to pull-migrate. This condition
> occurs during module unload, but can also occur as a denial-of-service
> using sys_sched_setaffinity(). Several hundred CPUs performing this
> fruitless load_balance() will livelock on the busiest CPU's runqueue
> lock. A smaller number of CPUs will livelock if the pinned task count
> gets high. This simple patch remedies the more common first problem:
> after a move_tasks() failure to migrate anything, the balance_interval
> increments. Using a simple increment, vs. the more dramatic doubling of
> the balance_interval, is conservative and yet also effective.
>
> John Hawkes
>
>
> Signed-off-by: John Hawkes <hawkes@sgi.com>
looks good to me.
Acked-by: Ingo Molnar <mingo@elte.hu>
Ingo
next prev parent reply other threads:[~2004-10-20 20:08 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-20 19:36 [PATCH, 2.6.9] improved load_balance() tolerance for pinned tasks John Hawkes
2004-10-20 19:59 ` Ingo Molnar [this message]
2004-10-22 13:08 ` Nick Piggin
2004-10-22 19:38 ` John Hawkes
[not found] ` <00ee01c4b870$030b80f0$6700a8c0@comcast.net>
2004-10-23 4:27 ` Nick Piggin
2004-10-25 16:02 ` John Hawkes
2004-10-25 23:59 ` Nick Piggin
2004-10-30 0:21 ` Matthew Dobson
-- strict thread matches above, loose matches on Subject: below --
2004-10-22 19:20 John Hawkes
2004-10-23 4:22 ` Nick Piggin
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