From: Raistlin <raistlin@linux.it>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
Chris Friesen <cfriesen@nortel.com>,
oleg@redhat.com, Frederic Weisbecker <fweisbec@gmail.com>,
Darren Hart <darren@dvhart.com>,
Johan Eker <johan.eker@ericsson.com>,
"p.faure" <p.faure@akatech.ch>,
linux-kernel <linux-kernel@vger.kernel.org>,
Claudio Scordino <claudio@evidence.eu.com>,
michael trimarchi <trimarchi@retis.sssup.it>,
Fabio Checconi <fabio@gandalf.sssup.it>,
Tommaso Cucinotta <cucinotta@sssup.it>,
Juri Lelli <juri.lelli@gmail.com>,
Nicola Manica <nicola.manica@disi.unitn.it>,
Luca Abeni <luca.abeni@unitn.it>,
Dhaval Giani <dhaval@retis.sssup.it>,
Harald Gustafsson <hgu1972@gmail.com>,
paulmck <paulmck@linux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 09/22] sched: add period support for -deadline tasks
Date: Fri, 12 Nov 2010 14:33:47 +0100 [thread overview]
Message-ID: <1289568827.6525.411.camel@Palantir> (raw)
In-Reply-To: <1289504635.2084.179.camel@laptop>
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On Thu, 2010-11-11 at 20:43 +0100, Peter Zijlstra wrote:
> > Since you spotted it... The biggest issue here is admission control
> > test. Right now this is done against task's bandwidth, i.e.,
> > sum_i(runtime_i/period_i)<=threshold, but it is unfortunately wrong...
> > Or at least very, very loose, to the point of being almost useless! :-(
>
> Right, I have some recollection on that.
>
:-)
> So sufficient (but not necessary) means its still a pessimistic approach
> but better than the one currently employed, or does it mean its
> optimistic and allows for unschedulable sets to be allowed in?
>
Tommaso already gave the best possible explanation of this! :-P
So, trying to recap:
- using runtime/min(deadline,period) _does_ guarantee schedulability,
but also rejects schedulable situations in UP/partitioning. Quite
sure it _does_not_ guarantee schedulability in SMP/global, but
*should* enable bounded tardiness;
- using runtime/period _does_not_ guarantee schedulability nor in
UP/partitioning neither in SMP/global, but *should* enable bounded
tardiness for _both_.
The *should*-s come from the fact that I feel like I read it somewhere,
but right now I can't find the paper(s), not even following the
references indicated by Bjorn and Jim in previous e-mails and threads
(i.e., I can't find anything _explicitly_ considering deadline!=period,
but it might be my fault)... :-(
Thus, all this being said, what do you want me to do? :-D
Since we care about bounded tardiness more than 100%-guaranteed
schedulability (which, BTW, neither min{} could give us, at least for
SMPs), should we stay with runtime/period? Tommaso, Luca, do you think
it would be so bad?
Thanks and Regards,
Dario
--
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa (Italy)
http://blog.linux.it/raistlin / raistlin@ekiga.net /
dario.faggioli@jabber.org
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next prev parent reply other threads:[~2010-11-12 13:34 UTC|newest]
Thread overview: 135+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-29 6:18 [RFC][PATCH 00/22] sched: SCHED_DEADLINE v3 Raistlin
2010-10-29 6:25 ` [RFC][PATCH 01/22] sched: add sched_class->task_dead Raistlin
2010-10-29 6:27 ` [RFC][PATCH 02/22] sched: add extended scheduling interface Raistlin
2010-11-10 16:00 ` Dhaval Giani
2010-11-10 16:12 ` Dhaval Giani
2010-11-10 22:45 ` Raistlin
2010-11-10 16:17 ` Claudio Scordino
2010-11-10 17:28 ` Peter Zijlstra
2010-11-10 19:26 ` Peter Zijlstra
2010-11-10 23:33 ` Tommaso Cucinotta
2010-11-11 12:19 ` Peter Zijlstra
2010-11-10 22:17 ` Raistlin
2010-11-10 22:57 ` Tommaso Cucinotta
2010-11-11 13:32 ` Peter Zijlstra
2010-11-11 13:54 ` Raistlin
2010-11-11 14:08 ` Peter Zijlstra
2010-11-11 17:27 ` Raistlin
2010-11-11 14:05 ` Dhaval Giani
2010-11-10 22:24 ` Raistlin
2010-11-10 18:50 ` Peter Zijlstra
2010-11-10 22:05 ` Raistlin
2010-11-12 16:38 ` Steven Rostedt
2010-11-12 16:43 ` Peter Zijlstra
2010-11-12 16:52 ` Steven Rostedt
2010-11-12 19:19 ` Raistlin
2010-11-12 19:23 ` Steven Rostedt
2010-11-12 17:42 ` Tommaso Cucinotta
2010-11-12 19:21 ` Steven Rostedt
2010-11-12 19:24 ` Raistlin
2010-10-29 6:28 ` [RFC][PATCH 03/22] sched: SCHED_DEADLINE data structures Raistlin
2010-11-10 18:59 ` Peter Zijlstra
2010-11-10 22:06 ` Raistlin
2010-11-10 19:10 ` Peter Zijlstra
2010-11-12 17:11 ` Steven Rostedt
2010-10-29 6:29 ` [RFC][PATCH 04/22] sched: SCHED_DEADLINE SMP-related " Raistlin
2010-11-10 19:17 ` Peter Zijlstra
2010-10-29 6:30 ` [RFC][PATCH 05/22] sched: SCHED_DEADLINE policy implementation Raistlin
2010-11-10 19:21 ` Peter Zijlstra
2010-11-10 19:43 ` Peter Zijlstra
2010-11-11 1:02 ` Raistlin
2010-11-10 19:45 ` Peter Zijlstra
2010-11-10 22:26 ` Raistlin
2010-11-10 20:21 ` Peter Zijlstra
2010-11-11 1:18 ` Raistlin
2010-11-11 13:13 ` Peter Zijlstra
2010-11-11 14:13 ` Peter Zijlstra
2010-11-11 14:28 ` Raistlin
2010-11-11 14:17 ` Peter Zijlstra
2010-11-11 18:33 ` Raistlin
2010-11-11 14:25 ` Peter Zijlstra
2010-11-11 14:33 ` Raistlin
2010-11-14 8:54 ` Raistlin
2010-11-23 14:24 ` Peter Zijlstra
2010-10-29 6:31 ` [RFC][PATCH 06/22] sched: SCHED_DEADLINE handles spacial kthreads Raistlin
2010-11-11 14:31 ` Peter Zijlstra
2010-11-11 14:50 ` Dario Faggioli
2010-11-11 14:34 ` Peter Zijlstra
2010-11-11 15:27 ` Oleg Nesterov
2010-11-11 15:43 ` Peter Zijlstra
2010-11-11 16:32 ` Oleg Nesterov
2010-11-13 18:35 ` Peter Zijlstra
2010-11-13 19:58 ` Oleg Nesterov
2010-11-13 20:31 ` Peter Zijlstra
2010-11-13 20:51 ` Peter Zijlstra
2010-11-13 23:31 ` Peter Zijlstra
2010-11-15 20:06 ` [PATCH] sched: Simplify cpu-hot-unplug task migration Peter Zijlstra
2010-11-17 19:27 ` Oleg Nesterov
2010-11-17 19:42 ` Peter Zijlstra
2010-11-18 14:05 ` Oleg Nesterov
2010-11-18 14:24 ` Peter Zijlstra
2010-11-18 15:32 ` Oleg Nesterov
2010-11-18 14:09 ` [tip:sched/core] " tip-bot for Peter Zijlstra
2010-11-11 14:46 ` [RFC][PATCH 06/22] sched: SCHED_DEADLINE handles spacial kthreads Peter Zijlstra
2010-10-29 6:32 ` [RFC][PATCH 07/22] sched: SCHED_DEADLINE push and pull logic Raistlin
2010-11-12 16:17 ` Peter Zijlstra
2010-11-12 21:11 ` Raistlin
2010-11-14 9:14 ` Raistlin
2010-11-23 14:27 ` Peter Zijlstra
2010-10-29 6:33 ` [RFC][PATCH 08/22] sched: SCHED_DEADLINE avg_update accounting Raistlin
2010-11-11 19:16 ` Peter Zijlstra
2010-10-29 6:34 ` [RFC][PATCH 09/22] sched: add period support for -deadline tasks Raistlin
2010-11-11 19:17 ` Peter Zijlstra
2010-11-11 19:31 ` Raistlin
2010-11-11 19:43 ` Peter Zijlstra
2010-11-11 23:33 ` Tommaso Cucinotta
2010-11-12 13:33 ` Raistlin [this message]
2010-11-12 13:45 ` Peter Zijlstra
2010-11-12 13:46 ` Luca Abeni
2010-11-12 14:01 ` Raistlin
2010-10-29 6:35 ` [RFC][PATCH 10/22] sched: add a syscall to wait for the next instance Raistlin
2010-11-11 19:21 ` Peter Zijlstra
2010-11-11 19:33 ` Raistlin
2010-10-29 6:35 ` [RFC][PATCH 11/22] sched: add schedstats for -deadline tasks Raistlin
2010-10-29 6:36 ` [RFC][PATCH 12/22] sched: add runtime reporting " Raistlin
2010-11-11 19:37 ` Peter Zijlstra
2010-11-12 16:15 ` Raistlin
2010-11-12 16:27 ` Peter Zijlstra
2010-11-12 21:12 ` Raistlin
2010-10-29 6:37 ` [RFC][PATCH 13/22] sched: add resource limits " Raistlin
2010-11-11 19:57 ` Peter Zijlstra
2010-11-12 21:30 ` Raistlin
2010-11-12 23:32 ` Peter Zijlstra
2010-10-29 6:38 ` [RFC][PATCH 14/22] sched: add latency tracing " Raistlin
2010-10-29 6:38 ` [RFC][PATCH 15/22] sched: add traceporints " Raistlin
2010-11-11 19:54 ` Peter Zijlstra
2010-11-12 16:13 ` Raistlin
2010-10-29 6:39 ` [RFC][PATCH 16/22] sched: add SMP " Raistlin
2010-10-29 6:40 ` [RFC][PATCH 17/22] sched: add signaling overrunning " Raistlin
2010-11-11 21:58 ` Peter Zijlstra
2010-11-12 15:39 ` Raistlin
2010-11-12 16:04 ` Peter Zijlstra
2010-10-29 6:42 ` [RFC][PATCH 19/22] rtmutex: turn the plist into an rb-tree Raistlin
2010-10-29 6:42 ` [RFC][PATCH 18/22] sched: add reclaiming logic to -deadline tasks Raistlin
2010-11-11 22:12 ` Peter Zijlstra
2010-11-12 15:36 ` Raistlin
2010-11-12 16:04 ` Peter Zijlstra
2010-11-12 17:41 ` Luca Abeni
2010-11-12 17:51 ` Peter Zijlstra
2010-11-12 17:54 ` Luca Abeni
2010-11-13 21:08 ` Raistlin
2010-11-12 18:07 ` Tommaso Cucinotta
2010-11-12 19:07 ` Raistlin
2010-11-13 0:43 ` Peter Zijlstra
2010-11-13 1:49 ` Tommaso Cucinotta
2010-11-12 18:56 ` Raistlin
[not found] ` <80992760-24F2-42AE-AF2D-15727F6A1C81@email.unc.edu>
2010-11-15 18:37 ` James H. Anderson
2010-11-15 19:23 ` Luca Abeni
2010-11-15 19:49 ` James H. Anderson
2010-11-15 19:39 ` Luca Abeni
2010-11-15 21:34 ` Raistlin
2010-10-29 6:43 ` [RFC][PATCH 20/22] sched: drafted deadline inheritance logic Raistlin
2010-11-11 22:15 ` Peter Zijlstra
2010-11-14 12:00 ` Raistlin
2010-10-29 6:44 ` [RFC][PATCH 21/22] sched: add bandwidth management for sched_dl Raistlin
2010-10-29 6:45 ` [RFC][PATCH 22/22] sched: add sched_dl documentation Raistlin
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