linux-kernel - Re: [PATCH] sched: select 'idle' cfs_rq per task-group to prevent tg-internal imbalance

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Message-ID: <20140702124918.GE19379@twins.programming.kicks-ass.net>
Date:	Wed, 2 Jul 2014 14:49:18 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Michael wang <wangyun@...ux.vnet.ibm.com>
Cc:	Mike Galbraith <umgwanakikbuti@...il.com>,
	Rik van Riel <riel@...hat.com>,
	Ingo Molnar <mingo@...nel.org>, Alex Shi <alex.shi@...aro.org>,
	Paul Turner <pjt@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: select 'idle' cfs_rq per task-group to prevent
 tg-internal imbalance

On Wed, Jul 02, 2014 at 10:47:34AM +0800, Michael wang wrote:
> The opinion on features actually make me a little confusing... I used to
> think the scheduler is willing on providing kinds of way to adapt itself
> to different situation, and some features do help on that, make them
> only a debug option make the scheduler more static to users, but I know
> that's not what I should touched...
> 
> Anyway, the problem is still there and seems like we have to adopt some
> optional solution to address it, we'll still working and practice on
> that, please let us know if you have any ideas we could help on ;-)

No, its very much not intended as a user knob to adapt.

The problem with that approach to scheduling is that one set of knobs
runs workload A, while another set of knobs runs workload B, but what
happens if you need to run both A and B on the same machine?

So optional things and knobs are a complete fail and will not happen.

Clearly I need to go take out all these things because people don't seem
to know this and SCHED_DEBUG isn't a big enough hint. Tedious.

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