From: Arjan van de Ven <arjan@linux.intel.com>
To: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Ingo Molnar <mingo@kernel.org>,
"alex.shi@intel.com" <alex.shi@intel.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"preeti@linux.vnet.ibm.com" <preeti@linux.vnet.ibm.com>,
"vincent.guittot@linaro.org" <vincent.guittot@linaro.org>,
"efault@gmx.de" <efault@gmx.de>,
"pjt@google.com" <pjt@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linaro-kernel@lists.linaro.org" <linaro-kernel@lists.linaro.org>,
"len.brown@intel.com" <len.brown@intel.com>,
"corbet@lwn.net" <corbet@lwn.net>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
catalin.marinas@arm.com
Subject: Re: power-efficient scheduling design
Date: Tue, 18 Jun 2013 08:20:28 -0700 [thread overview]
Message-ID: <51C07ABC.2080704@linux.intel.com> (raw)
In-Reply-To: <20130614160522.GG32728@e103034-lin>
On 6/14/2013 9:05 AM, Morten Rasmussen wrote:
> Looking at the discussion it seems that people have slightly different
> views, but most agree that the goal is an integrated scheduling,
> frequency, and idle policy like you pointed out from the beginning.
... except that such a solution does not really work for Intel hardware.
The OS does not get to really pick the CPU "frequency" (never mind that
frequency is not what gets controlled), the hardware picks the frequency.
The OS can do some level of requests (best to think of this as a percentage
more than frequency) but what you actually get is more often than not
what you asked for.
You can look in hindsight what kind of performance you got (from some basic
counters in MSRs), and the scheduler can use that to account backwards to what some process
got. But to predict what you will get in the future...... that's near impossible
on any realistic system nowadays (and even more so in the future).
Treating "frequency" (well "performance) and idle separately is also a false thing to do
(yes I know in 3.9/3.10 we still do that for Intel hw, but we're working
on fixing that). They are by no means separate things. One guy's idle state
is the other guys power budget (and thus performance)!.
next prev parent reply other threads:[~2013-06-18 15:20 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-30 13:47 [RFC] Comparison of power-efficient scheduling patch sets Morten Rasmussen
2013-05-31 1:17 ` Alex Shi
2013-05-31 8:23 ` Alex Shi
2013-05-31 10:52 ` power-efficient scheduling design Ingo Molnar
2013-06-03 14:59 ` Arjan van de Ven
2013-06-03 15:43 ` Ingo Molnar
2013-06-04 15:03 ` Morten Rasmussen
2013-06-07 6:26 ` Preeti U Murthy
2013-06-20 15:23 ` Ingo Molnar
2013-06-05 9:56 ` Amit Kucheria
2013-06-07 6:03 ` Preeti U Murthy
2013-06-07 14:51 ` Catalin Marinas
2013-06-07 18:08 ` Preeti U Murthy
2013-06-07 17:36 ` David Lang
2013-06-09 4:33 ` Preeti U Murthy
2013-06-08 11:28 ` Catalin Marinas
2013-06-08 14:02 ` Rafael J. Wysocki
2013-06-09 3:42 ` Preeti U Murthy
2013-06-09 22:53 ` Catalin Marinas
2013-06-10 16:25 ` Daniel Lezcano
2013-06-12 0:27 ` David Lang
2013-06-12 1:48 ` Arjan van de Ven
2013-06-12 9:48 ` Amit Kucheria
2013-06-12 16:22 ` David Lang
2013-06-12 10:20 ` Catalin Marinas
2013-06-12 15:24 ` Arjan van de Ven
2013-06-12 17:04 ` Catalin Marinas
2013-06-12 9:50 ` Daniel Lezcano
2013-06-12 16:30 ` David Lang
2013-06-11 0:50 ` Rafael J. Wysocki
2013-06-13 4:32 ` Preeti U Murthy
2013-06-09 4:23 ` Preeti U Murthy
2013-06-07 15:23 ` Arjan van de Ven
2013-06-14 16:05 ` Morten Rasmussen
2013-06-17 11:23 ` Catalin Marinas
2013-06-18 1:37 ` David Lang
2013-06-18 10:23 ` Morten Rasmussen
2013-06-18 17:39 ` David Lang
2013-06-19 12:39 ` Morten Rasmussen
2013-06-18 15:20 ` Arjan van de Ven [this message]
2013-06-18 17:47 ` David Lang
2013-06-18 19:36 ` Arjan van de Ven
2013-06-19 15:39 ` Arjan van de Ven
2013-06-19 17:00 ` Morten Rasmussen
2013-06-19 17:08 ` Arjan van de Ven
2013-06-21 8:50 ` Morten Rasmussen
2013-06-21 15:29 ` Arjan van de Ven
2013-06-21 15:38 ` Arjan van de Ven
2013-06-21 21:23 ` Catalin Marinas
2013-06-21 21:34 ` Arjan van de Ven
2013-06-23 23:32 ` Benjamin Herrenschmidt
2013-06-24 10:07 ` Catalin Marinas
2013-06-24 15:26 ` Arjan van de Ven
2013-06-24 21:59 ` Benjamin Herrenschmidt
2013-06-24 23:10 ` Arjan van de Ven
2013-06-18 19:06 ` Catalin Marinas
2013-06-21 15:06 ` Morten Rasmussen
2013-06-23 10:55 ` Ingo Molnar
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