From: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Ankita Garg <ankita@in.ibm.com>,
linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
linux-pm@lists.linux-foundation.org, thomas.abraham@linaro.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Matthew Garrett <mjg59@srcf.ucam.org>,
Arjan van de Ven <arjan@infradead.org>
Subject: Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management
Date: Wed, 29 Jun 2011 23:37:33 +0530 [thread overview]
Message-ID: <20110629180733.GF3646@dirshya.in.ibm.com> (raw)
In-Reply-To: <1309367184.11430.594.camel@nimitz>
* Dave Hansen <dave@linux.vnet.ibm.com> [2011-06-29 10:06:24]:
> I was kinda hoping for something a bit simpler than that. I'd boil down
> what you were saying to this:
>
> 1. The kernel must be aware of how the pieces of hardware are
> mapped in to the system's physical address space
> 2. The kernel must have a mechanism in place to minimize access to
> specific pieces of hardware
(mainly by controlling allocations and reclaim)
> 3. For destructive power-down operations, the kernel should have a
> mechanism in place to ensure that no valuable data is contained
> in the memory to be powered down.
>
> Is that complete?
At a high level these are the main requirements, except that different
operations/features can happen at different/higher granularity. The
infrastructure should be able to related groups of regions and act
upon for a specific optimization. Like granularity for (2) may be
512MB, while (3) could be a pair of 512MB blocks. This is relatively
a minor issue to solve.
> On Wed, 2011-06-29 at 18:30 +0530, Ankita Garg wrote:
> > 1) Dynamic Power Transition: The memory controller can have the ability
> > to automatically transition regions of memory into lower power states
> > when they are devoid of references for a pre-defined threshold amount of
> > time. Memory contents are preserved in the low power states and accessing
> > memory that is at a low power state takes a latency hit.
> >
> > 2) Dynamic Power Off: If a region is free/unallocated, the software can
> > indicate to the controller to completely turn off power to a certain
> > region. Memory contents are lost and hence the software has to be
> > absolutely sure about the usage statistics of the particular region. This
> > is a runtime capability, where the required amount of memory can be
> > powered 'ON' to match the workload demands.
> >
> > 3) Partial Array Self-Refresh (PASR): If a certain regions of memory is
> > free/unallocated, the software can indicate to the controller to not
> > refresh that region when the system goes to suspend-to-ram state and
> > thereby save standby power consumption.
>
> (3) is simply a subset of (2), but with the additional restriction that
> the power off can only occur during a suspend operation.
>
> Let's say we fully implemented support for (2). What would be missing
> to support PASR?
The similarity between (2) and (3) here is the need for accurate
statistics to know allocation status. The difference is the
actuation/trigger part... in case of (2) the trigger would happen
during allocation/free while in case of (3) it happens only at suspend
time. Also the granularity could be different, generally PASR is very
fine grain as compared for power-off at controller level.
We can combine them and look at just how to track allocations at
different (or multiple) physical boundaries.
--Vaidy
next prev parent reply other threads:[~2011-06-29 18:07 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-27 12:31 [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management Ankita Garg
2011-05-27 12:31 ` [PATCH 01/10] mm: Introduce the memory regions data structure Ankita Garg
2011-05-27 15:30 ` Dave Hansen
2011-05-27 18:20 ` Vaidyanathan Srinivasan
2011-05-27 21:31 ` Dave Hansen
2011-05-29 8:16 ` Ankita Garg
2011-05-31 17:34 ` Dave Hansen
2011-06-02 8:54 ` Ankita Garg
2011-05-27 12:31 ` [PATCH 02/10] mm: Helper routines Ankita Garg
2011-05-27 12:31 ` [PATCH 03/10] mm: Init zones inside memory regions Ankita Garg
2011-05-27 12:31 ` [PATCH 04/10] mm: Refer to zones from " Ankita Garg
2011-05-27 12:31 ` [PATCH 05/10] mm: Create zonelists Ankita Garg
2011-05-27 12:31 ` [PATCH 06/10] mm: Verify zonelists Ankita Garg
2011-05-27 12:31 ` [PATCH 07/10] mm: Modify vmstat Ankita Garg
2011-05-27 12:31 ` [PATCH 08/10] mm: Modify vmscan Ankita Garg
2011-05-27 12:31 ` [PATCH 09/10] mm: Reflect memory region changes in zoneinfo Ankita Garg
2011-05-27 12:31 ` [PATCH 10/10] mm: Create memory regions at boot-up Ankita Garg
2011-05-28 14:39 ` Jean-Christophe PLAGNIOL-VILLARD
2011-05-28 7:56 ` [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management Andrew Morton
2011-05-28 13:16 ` Ankita Garg
2011-06-09 18:52 ` Paul E. McKenney
2011-06-10 0:51 ` Kyungmin Park
2011-06-10 15:11 ` Paul E. McKenney
2011-06-10 15:59 ` Matthew Garrett
2011-06-10 16:55 ` Paul E. McKenney
2011-06-10 17:05 ` Matthew Garrett
2011-06-10 17:19 ` Paul E. McKenney
2011-06-10 17:23 ` Matthew Garrett
2011-06-10 17:52 ` Paul E. McKenney
2011-06-10 18:08 ` Matthew Garrett
2011-06-10 18:47 ` Paul E. McKenney
2011-06-10 19:23 ` Matthew Garrett
2011-06-10 19:37 ` Paul E. McKenney
2011-06-10 20:12 ` Matthew Garrett
2011-06-11 3:02 ` Arjan van de Ven
2011-06-11 17:06 ` Paul E. McKenney
2011-06-11 17:26 ` Arjan van de Ven
2011-06-12 23:07 ` Paul E. McKenney
2011-06-13 14:28 ` Arjan van de Ven
2011-06-13 23:04 ` Paul E. McKenney
2011-06-14 8:51 ` Ankita Garg
2011-06-15 16:53 ` Ankita Garg
2011-06-18 4:08 ` Arjan van de Ven
2011-06-10 17:33 ` Ankita Garg
2011-06-11 17:08 ` Paul E. McKenney
2011-07-12 5:31 ` amit kachhap
2011-06-13 4:47 ` KAMEZAWA Hiroyuki
2011-06-16 4:20 ` Ankita Garg
2011-06-16 9:12 ` KAMEZAWA Hiroyuki
2011-06-17 15:28 ` Ankita Garg
2011-06-19 23:53 ` KAMEZAWA Hiroyuki
2011-06-16 16:04 ` Dave Hansen
2011-06-17 10:03 ` Ankita Garg
2011-06-29 13:00 ` Ankita Garg
2011-06-29 17:06 ` Dave Hansen
2011-06-29 17:42 ` Ankita Garg
2011-06-29 17:59 ` Dave Hansen
2011-06-29 18:17 ` Vaidyanathan Srinivasan
2011-06-30 4:37 ` Ankita Garg
2011-06-29 20:11 ` Andi Kleen
2011-06-30 5:11 ` Ankita Garg
2011-06-29 18:07 ` Vaidyanathan Srinivasan [this message]
2011-07-06 8:45 ` Pekka Enberg
2011-07-06 9:01 ` Pekka Enberg
2011-07-06 16:50 ` Vaidyanathan Srinivasan
2011-07-06 16:41 ` Vaidyanathan Srinivasan
2011-07-06 20:20 ` david
2011-07-07 4:54 ` Ankita Garg
2011-07-07 18:00 ` Pekka Enberg
2011-07-08 1:32 ` david
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