linux-kernel - Re: [PATCH 3/7] idle, thermal, acpi: Remove home grown idle implementations

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Message-ID: <528E32EF.2050300@linux.intel.com>
Date:	Thu, 21 Nov 2013 08:21:03 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	paulmck@...ux.vnet.ibm.com, Peter Zijlstra <peterz@...radead.org>
CC:	Jacob Pan <jacob.jun.pan@...ux.intel.com>, lenb@...nel.org,
	rjw@...ysocki.net, Eliezer Tamir <eliezer.tamir@...ux.intel.com>,
	Chris Leech <christopher.leech@...el.com>,
	David Miller <davem@...emloft.net>, rui.zhang@...el.com,
	Mike Galbraith <bitbucket@...ine.de>,
	Ingo Molnar <mingo@...nel.org>, hpa@...or.com,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 3/7] idle, thermal, acpi: Remove home grown idle implementations

On 11/21/2013 8:07 AM, Paul E. McKenney wrote:
> As long as RCU has some reliable way to identify an idle task, I am
> good.  But I have to ask -- why can't idle injection coordinate with
> the existing idle tasks rather than temporarily making alternative
> idle tasks?

it's not a real idle. that's the whole problem of the situation.
to the rest of the OS, this is being BUSY (busy saving power using
a CPU instruction, but it might as well have been an mdelay() operation)
and it's also what end users expect; they want to be able to see
where there performance (read: cpu time in "top") is going.

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