From: Peter Zijlstra <peterz@infradead.org>
To: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Cc: Dhaval Giani <dhaval.giani@gmail.com>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Dario Faggioli <faggioli@gandalf.sssup.it>,
Fabio Checconi <fabio@gandalf.sssup.it>,
linux-kernel@vger.kernel.org
Subject: Re: 1 RT task blocks 4-core machine ?
Date: Wed, 06 Oct 2010 15:34:05 +0200 [thread overview]
Message-ID: <1286372045.2144.180.camel@laptop> (raw)
In-Reply-To: <4CAA54A1.6050507@sssup.it>
On Tue, 2010-10-05 at 00:26 +0200, Tommaso Cucinotta wrote:
> A possible explanation might be that the CFS load balancing logic sees
> my only active task (e.g., the ssh server or shell etc.) as running
> alone on its core, and does not detect that it is inhibited to actually
> run due to RT tasks on the same core. Therefore, it will not migrate
> the task to the free cores. Does this explanation make sense
> or is it completely wrong ?
Possibly, its got some logic to detect this but maybe it gets confused
still, in particular look at the adaptive cpu_power in
update_cpu_power() and calling functions.
> Also, I'd like to hear whether this is considered the "normal/desired"
> behavior of intermixing RT and non-RT tasks.
Pegging a cpu using sched_fifo/rr pretty much means you get to keep the
pieces, if it works nice, if you can make it work better kudos, but no
polling from sched_fifo/rr is not something that is considered sane for
the general health of your system.
next prev parent reply other threads:[~2010-10-06 13:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <AANLkTim2icGqFWB1S6TVcQwmo+sCcGdNDPO3s8LFqzR=@mail.gmail.com>
2010-10-04 22:26 ` 1 RT task blocks 4-core machine ? Tommaso Cucinotta
2010-10-06 13:34 ` Peter Zijlstra [this message]
2010-10-09 17:42 Tommaso Cucinotta
2010-10-11 7:53 ` Peter Zijlstra
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