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Date: Tue, 13 Mar 2012 14:18:21 -0400
Message-ID: <CA+czFiCcDMz7nMhfabGL6iRL4ecd+cxWdhu3ZeGSQeJf_MKM1Q@mail.gmail.com>
Subject: Re: [gentoo-user] hard drive encryption
From: Michael Mol <mikemol@gmail.com>
To: gentoo-user@lists.gentoo.org
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On Tue, Mar 13, 2012 at 2:06 PM, Florian Philipp <lists@binarywings.net> wrote:
> Am 13.03.2012 18:45, schrieb Frank Steinmetzger:
>> On Tue, Mar 13, 2012 at 05:11:47PM +0100, Florian Philipp wrote:
>>
>>>> Since I am planning to encrypt only home/ under LVM control, what kind
>>>> of overhead should I expect?
>>>
>>> What do you mean with overhead? CPU utilization? In that case the
>>> overhead is minimal, especially when you run a 64-bit kernel with the
>>> optimized AES kernel module.
>>
>> Speaking of that...
>> I always wondered what the exact difference was between AES and AES i586. I
>> can gather myself that it's about optimisation for a specific architecture.
>> But which one would be best for my i686 Core 2 Duo?
>
> From what I can see in the kernel sources, there is a generic AES
> implementation using nothing but portable C code and then there is
> "aes-i586" assembler code with "aes_glue" C code.
> So I assume the i586
> version is better for you --- unless GCC suddenly got a lot better at
> optimizing code.
Since when, exactly? GCC isn't the best compiler at optimization, but
I fully expect current versions to produce better code for x86-64 than
hand-tuned i586. Wider registers, more registers, crypto acceleration
instructions and SIMD instructions are all very nice to have. I don't
know the specifics of AES, though, or what kind of crypto algorithm it
is, so it's entirely possible that one can't effectively parallelize
it except in some relatively unique circumstances.
--
:wq