linux-kernel - Re: [CRYPTO] is it really optimized ?

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Message-ID: <38b2ab8a0704171024m3d838bdak14370a7d0931557f@mail.gmail.com>
Date:	Tue, 17 Apr 2007 19:24:04 +0200
From:	"Francis Moreau" <francis.moro@...il.com>
To:	"Roland Dreier" <rdreier@...co.com>
Cc:	"Herbert Xu" <herbert@...dor.apana.org.au>,
	helge.hafting@...el.hist.no, linux-kernel@...r.kernel.org,
	linux-crypto@...r.kernel.org
Subject: Re: [CRYPTO] is it really optimized ?

On 4/17/07, Roland Dreier <rdreier@...co.com> wrote:
>  > > I wonder if there's some way you can cache the last caller and reload
>  > > the key lazily (only when it changes).
>  >
>  > yes something that allows crypto drivers to detect if the key has
>  > changed would be good.
>
> It seems trivial to keep the last key you were given and do a quick
> memcmp in your setkey method to see if it's different from the last
> key you pushed to hardware, and set a flag if it is.  Then only do
> your set_key() if you have a new key to pass to hardware.
>
> I'm assuming the expense is in the aes_write() calls, and you could
> avoid them if you know you're not writing something new.
>

that's a wrong assumption. aes_write()/aes_read() are both used to
access to the controller and are slow (no cache involved).

thanks
-- 
Francis
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