Message-ID: <52438A6B.30202@linux.intel.com>
Date: Wed, 25 Sep 2013 18:14:19 -0700
From: Arjan van de Ven <arjan@linux.intel.com>
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To: Andi Kleen <andi@firstfloor.org>
CC: Andrew Morton <akpm@linux-foundation.org>,
        "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>, mgorman@suse.de,
        dave@sr71.net, hannes@cmpxchg.org, tony.luck@intel.com,
        matthew.garrett@nebula.com, riel@redhat.com,
        srinivas.pandruvada@linux.intel.com, willy@linux.intel.com,
        kamezawa.hiroyu@jp.fujitsu.com, lenb@kernel.org, rjw@sisk.pl,
        gargankita@gmail.com, paulmck@linux.vnet.ibm.com,
        svaidy@linux.vnet.ibm.com, isimatu.yasuaki@jp.fujitsu.com,
        santosh.shilimkar@ti.com, kosaki.motohiro@gmail.com,
        linux-pm@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [Results] [RFC PATCH v4 00/40] mm: Memory Power Management
References: <20130925231250.26184.31438.stgit@srivatsabhat.in.ibm.com> <52437128.7030402@linux.vnet.ibm.com> <20130925164057.6bbaf23bdc5057c42b2ab010@linux-foundation.org> <20130925234734.GK18242@two.firstfloor.org>
In-Reply-To: <20130925234734.GK18242@two.firstfloor.org>
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On 9/25/2013 4:47 PM, Andi Kleen wrote:
>> Also, the changelogs don't appear to discuss one obvious downside: the
>> latency incurred in bringing a bank out of one of the low-power states
>> and back into full operation.  Please do discuss and quantify that to
>> the best of your knowledge.
>
> On Sandy Bridge the memry wakeup overhead is really small. It's on by default
> in most setups today.

yet grouping is often defeated (in current systems) due to hw level interleaving ;-(
sometimes that's a bios setting though.

in internal experimental bioses we've been able to observe a "swing" of a few watts
(not with these patches but with some other tricks)...
I'm curious to see how these patches do for Srivatsa

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