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From: Alfred Perlstein <bright@mu.org>
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To: Konstantin Belousov <kostikbel@gmail.com>
Subject: Re: Unmapped I/O
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Cc: Ivan Voras <ivoras@freebsd.org>, freebsd-arch@freebsd.org
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On 12/21/12 4:02 AM, Konstantin Belousov wrote:
> On Fri, Dec 21, 2012 at 12:52:35PM +0100, Ivan Voras wrote:
>> On 20 December 2012 21:15, Konstantin Belousov <kostikbel@gmail.com> wrote:
>>
>>> Nothing is changed for existing GEOM classes, and it does not mean anything
>>> for GEOM developers, unless she wants to change the GEOM class to handle
>>> unmapped BIOs.
>> Understood, but the intention of my question was: do you recommend
>> GEOM classes should take the effort and implement unmapped BIOs
>> whenever possible?
> Depends. RAID 0 and RAID 1 can process unmapped BIOs without changes,
> I am sure. For the class like RAID5, you would need a hardware
> for it to be able to operate on the unmapped BIOs without requiring
> the remap. There is indeed Intel IOAT, which I believe can do this.
>
> On the other hand, for encrypting classes like GELI it probably does not
> make much sense to care, for the case of encryption done in software or
> using AES-NI.

*Raising my hand like the annoying kid in class*

What about asking for the physaddr for such pages on dmap arches?

by the way, thanks for this giant leap forward, it's going to help 
FreeBSD very much!

-Alfred