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To: John-Mark Gurney <jmg@funkthat.com>
Subject: Re: always load aesni or load it when cpu supports it
In-reply-to: <20131021184310.GZ56872@funkthat.com>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
References: <20131020070022.GP56872@funkthat.com>
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Date: Mon, 21 Oct 2013 18:45:02 +0000
Message-ID: <37850.1382381102@critter.freebsd.dk>
Cc: Andre Oppermann <andre@freebsd.org>, Mark R V Murray <mark@grondar.org>,
 freebsd-arch@freebsd.org
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In message <20131021184310.GZ56872@funkthat.com>, John-Mark Gurney writes:
>Poul-Henning Kamp wrote this message on Mon, Oct 21, 2013 at 18:32 +0000:

>Also depends upon the crypto mode you are using...  If you're using
>CBC encrypt, then you'd need a very fancy accelerator to out perform
>a CPU, but in other modes like XTS or CTR, an accelerator can/will out
>perform the CPU...

Only for very large requests that can amortize the considerable
setup overhead.

Either way, we do *not* want the heuristics to guess this spread out
over every and all modules which need crypto services.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.