linux-kernel - Re: [sched-devel, patch-rfc] rework of "prioritizenon-migratabletasks over migratable ones"

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Message-Id: <4858BEA3.BA47.005A.0@novell.com>
Date:	Wed, 18 Jun 2008 05:52:03 -0600
From:	"Gregory Haskins" <ghaskins@...ell.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Dmitry Adamushko" <dmitry.adamushko@...il.com>,
	"Steven Rostedt" <rostedt@...dmis.org>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [sched-devel, patch-rfc] rework of
	"prioritizenon-migratabletasks over migratable ones"

>>> On Wed, Jun 18, 2008 at  6:39 AM, in message <20080618103919.GH15255@...e.hu>,
Ingo Molnar <mingo@...e.hu> wrote: 

> * Gregory Haskins <ghaskins@...ell.com> wrote:
> 
>> >>> On Mon, Jun 16, 2008 at  3:17 PM, in message
>> <1213643862.16944.142.camel@...ns>, Peter Zijlstra <a.p.zijlstra@...llo.nl>
>> wrote: 
>> > On Mon, 2008-06-16 at 19:59 +0200, Dmitry Adamushko wrote:
>> > 
>> >> One way or another, we have different aritifacts (and mine have likely
>> >> more) but conceptually, both "violates" POSIX if a strict round-robin
>> >> scheduling is required.
>> > 
>> > 
> http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_08.html#t
>> > ag_02_08_04_01
>> > 
>> > Is quite strict on what FIFO should do, and I know of two points where
>> > we deviate and should work to match.
>> 
>> Thanks for the link, Peter.  When you read that, its pretty clear that 
>> this whole concept violates the standard.  Its probably best to just 
>> revert the patch and be done with it.
> 
> no, there's no spec violation here - the spec is silent on SMP issues.
> 
> the spec should not be read to force a global runqueue for RT tasks. 
> That would be silly beyond imagination.
> 
> so ... lets apply Dmitry's nice simplification, hm?

Hmm...I guess that is a good way to look at it.  Sounds good, thanks!

Perhaps I will write up a patch against his that fixes that suboptimal detection problem that he highlighted, afterall

Thanks,
-Greg


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