Message-ID: <4ABD4839.7060508@nortel.com>
Date: Fri, 25 Sep 2009 16:46:17 -0600
From: "Chris Friesen" <cfriesen@nortel.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Michael Trimarchi <trimarchi@gandalf.sssup.it>,
       sat <takeuchi_satoru@jp.fujitsu.com>,
       lkml <linux-kernel@vger.kernel.org>, Con Kolivas <kernel@kolivas.org>,
       Ingo Molnar <mingo@elte.hu>, Raistlin <raistlin@linux.it>
Subject: Re: massive_intr on CFS, BFS, and EDF
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On 09/25/2009 04:37 PM, Peter Zijlstra wrote:
> On Fri, 2009-09-25 at 15:31 -0600, Chris Friesen wrote:

>> Do you allow oversubscription with EDF?  It would seem so based on these
>> results.  Would it maybe make sense to disallow oversubscription, or
>> make it an option?
> 
> afaiu he doesn't, he simply splits the task's wcet between parent and
> child and (intends?) to feed back on child exit.

How does this work if we have one parent task that forks off a bunch of
kids like massive_intr?  Does each child get half the bandwidth of the
previous child?

> oversubscribing edf isn't in general recommended, iirc u>1 gives
> unbounded latencies with edf.

Right...so would it perhaps be more interesting to try a modified test
where each child's bandwidth is equal and small enough that there is no
oversubscription?

Chris
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