linux-kernel - Re: [Results] [RFC PATCH v4 00/40] mm: Memory Power Management

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 26 Sep 2013 18:46:31 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Arjan van de Ven <arjan@...ux.intel.com>
CC:	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>, mgorman@...e.de,
	dave@...1.net, hannes@...xchg.org, tony.luck@...el.com,
	matthew.garrett@...ula.com, riel@...hat.com,
	srinivas.pandruvada@...ux.intel.com, willy@...ux.intel.com,
	kamezawa.hiroyu@...fujitsu.com, lenb@...nel.org, rjw@...k.pl,
	gargankita@...il.com, paulmck@...ux.vnet.ibm.com,
	svaidy@...ux.vnet.ibm.com, isimatu.yasuaki@...fujitsu.com,
	santosh.shilimkar@...com, kosaki.motohiro@...il.com,
	linux-pm@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, maxime.coquelin@...ricsson.com,
	loic.pallardy@...ricsson.com, thomas.abraham@...aro.org,
	amit.kachhap@...aro.org
Subject: Re: [Results] [RFC PATCH v4 00/40] mm: Memory Power Management

On 09/26/2013 06:45 AM, Arjan van de Ven wrote:
> 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.
> 
> btw note that those kind of memory power savings are content-preserving,
> so likely a whole chunk of these patches is not actually needed on SNB
> (or anything else Intel sells or sold)
> 

Umm, why not? By consolidating the allocations to fewer memory regions,
this patchset also indirectly consolidates the *references* as well. And
its the lack of memory references that really makes the hardware transition
the unreferenced banks to low-power (content-preserving) states. So from what
I understand, this patchset should provide noticeable benefits on Intel/SNB
platforms as well.

(BTW, even in the prototype powerpc hardware that I mentioned, the primary
memory power savings is expected to come from content-preserving states. So
its not like this patchset was designed only for content-losing/full-poweroff
type of scenarios).

Regards,
Srivatsa S. Bhat

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/