linux-kernel - Re: [RFC][PATCH v5 00/14] sched: packing tasks

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Date:	Mon, 11 Nov 2013 08:39:45 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Catalin Marinas <catalin.marinas@....com>
CC:	Vincent Guittot <vincent.guittot@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Paul Turner <pjt@...gle.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Tony Luck <tony.luck@...el.com>,
	"alex.shi@...el.com" <alex.shi@...el.com>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"len.brown@...el.com" <len.brown@...el.com>,
	l.majewski@...sung.com, Jonathan Corbet <corbet@....net>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	linux-pm@...r.kernel.org
Subject: Re: [RFC][PATCH v5 00/14] sched: packing tasks


> I think the scheduler simply wants to say: we expect to go idle for X
> ns, we want a guaranteed wakeup latency of Y ns -- go do your thing.

as long as Y normally is "large" or "infinity" that is ok ;-)
(a smaller Y will increase power consumption and decrease system performance)



> I think you also raised the point in that we do want some feedback as to
> the cost of waking up particular cores to better make decisions on which
> to wake. That is indeed so.

having a hardware driver give a prefered CPU ordering for wakes can indeed be useful.
(I'm doubtful that changing the recommendation for each idle is going to pay off,
but proof is in the pudding; there are certainly long term effects where this can help)

>

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