linux-kernel - Re: gigabit ethernet power consumption

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Message-Id: <E1Ig9wz-0000sg-Ep@be1.lrz>
Date:	Fri, 12 Oct 2007 04:08:29 +0200
From:	Bodo Eggert <7eggert@....de>
To:	Kok@...r.kernel.org, Auke <auke-jan.h.kok@...el.com>,
	prasad@...ux.vnet.ibm.com,
	Lennart Sorensen <lsorense@...lub.uwaterloo.ca>,
	Pavel Machek <pavel@....cz>,
	Arjan van de Ven <arjan@...radead.org>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: gigabit ethernet power consumption

Kok, Auke <auke-jan.h.kok@...el.com> wrote:
> K.Prasad wrote:

>> Without the side-effect of experiencing a link-flap when switching to a
>> lower-speed (with its toll in terms of down-time for auto-negotiation,
>> STP, etc), the Interrupt Moderation Algorithm dynamically adjusts the
>> number of interrupts based on traffic - and presumably consume less
>> power. For an "Optimise for Power" kind of profile - the driver can be
>> loaded with a higher throttle rate during boot-time.
> 
> We're changing this to be run-time adjustable in newer drivers.
> 
> However, the power consumed by your nic staying in gigabit mode is much
> greater in the long run then what you can save by trying to scrounge for
> milliwatts reducing interrupts generated by the nic. By default it already
> moderates them somewhat. Practically this feature is really not useful for
> powersaving, it just won't add up to actual benefits in a real life situtation
> I think.

Just a thought:
How much power does a non-connected NIC consume, and can you save power
by forcing 10 MBit until a link is detected (doubling negotiation time)?
-- 
Top 100 things you don't want the sysadmin to say:
22. hey, what does mkfs do?

Friß, Spammer: 9nnbse9@...rp.7eggert.dyndns.org
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