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From: "Brown, Len" <len.brown@intel.com>
To: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Preeti U Murthy <preeti@linux.vnet.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Preeti Murthy <preeti.lkml@gmail.com>,
	"mingo@redhat.com" <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	LKML <linux-kernel@vger.kernel.org>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	Lists linaro-kernel <linaro-kernel@lists.linaro.org>
Subject: RE: [RFC PATCH 3/3] idle: store the idle state index in the struct rq
Date: Sat, 1 Feb 2014 19:39:29 +0000	[thread overview]
Message-ID: <1A7043D5F58CCB44A599DFD55ED4C948452D3706@FMSMSX106.amr.corp.intel.com> (raw)
In-Reply-To: <alpine.LFD.2.11.1402011028400.2312@knanqh.ubzr>

> And your point is?

It is a bad idea for an individual CPU to track the C-state
of another CPU, which can change the cycle after it was checked.
We know it is a bad idea because we used to do it,
until we realized code here can easily impact the
performance critical path.

In general, it is the OS's job to communicate constraints
to the HW, and the HW to act on them.  Not all HW is smart,
so sometimes the OS has to do more hand-holding -- but
less is more.

thanks,
-Len


  reply	other threads:[~2014-02-01 19:39 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-30 14:09 [RFC PATCH 0/3] cpuidle/sched: move main idle function in the idle.c Daniel Lezcano
2014-01-30 14:09 ` [RFC PATCH 1/3] cpuidle: split cpuidle_idle_call main function into functions Daniel Lezcano
2014-01-30 15:27   ` Peter Zijlstra
2014-01-30 15:39     ` Daniel Lezcano
2014-01-30 19:39   ` Nicolas Pitre
2014-01-31 14:10     ` Daniel Lezcano
2014-01-30 14:09 ` [RFC PATCH 2/3] cpuidle: move the cpuidle_idle_call function to idle.c Daniel Lezcano
2014-01-30 19:42   ` Nicolas Pitre
2014-01-30 14:09 ` [RFC PATCH 3/3] idle: store the idle state index in the struct rq Daniel Lezcano
2014-01-30 15:31   ` Peter Zijlstra
2014-01-30 16:27     ` Daniel Lezcano
2014-01-30 16:35       ` Peter Zijlstra
2014-01-30 17:25         ` Daniel Lezcano
2014-01-30 17:50           ` Lorenzo Pieralisi
2014-01-30 21:02             ` Nicolas Pitre
2014-01-31  9:46               ` Vincent Guittot
2014-01-31 10:04               ` Lorenzo Pieralisi
2014-01-31 10:44               ` Daniel Lezcano
2014-01-31  8:45           ` Preeti Murthy
2014-01-31  9:02             ` Peter Zijlstra
2014-01-31  9:39               ` Preeti U Murthy
2014-01-31 10:24                 ` Peter Zijlstra
2014-01-31 14:04                 ` Daniel Lezcano
2014-01-31 14:12                   ` Dietmar Eggemann
2014-01-31 15:07                 ` Arjan van de Ven
2014-01-31 15:37                   ` Daniel Lezcano
2014-01-31 15:50                     ` Arjan van de Ven
2014-01-31 16:35                       ` Daniel Lezcano
2014-01-31 16:42                         ` Arjan van de Ven
2014-01-31 18:19                       ` Nicolas Pitre
2014-02-01  6:00                         ` Brown, Len
2014-02-01 15:31                           ` Nicolas Pitre
2014-02-01 19:39                             ` Brown, Len [this message]
2014-02-01 20:13                               ` Nicolas Pitre
2014-02-01 15:40                           ` Lorenzo Pieralisi
2014-02-03 12:54                         ` Morten Rasmussen
2014-02-03 14:38                           ` Arjan van de Ven
2014-02-03 14:56                             ` Peter Zijlstra
2014-02-03 16:17                               ` Arjan van de Ven
2014-02-11 16:41                                 ` Peter Zijlstra
2014-02-11 17:12                                   ` Arjan van de Ven
2014-02-11 19:47                                     ` Peter Zijlstra
2014-02-12 15:16                                 ` Lorenzo Pieralisi
2014-02-12 16:14                                   ` Arjan van de Ven
2014-02-12 17:37                                     ` Lorenzo Pieralisi
2014-02-12 19:05                                       ` Nicolas Pitre
2014-02-04  9:14                               ` Ingo Molnar
2014-02-04 14:53                                 ` Arjan van de Ven
2014-02-04 14:56                                 ` Arjan van de Ven
2014-02-03 14:58                           ` Nicolas Pitre
2014-01-31 10:15             ` Daniel Lezcano
2014-02-03  6:33               ` Preeti U Murthy

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