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Re: [RFC] Replace scatterlist with crypto_frag

To: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [RFC] Replace scatterlist with crypto_frag
From: Evgeniy Polyakov <johnpol@xxxxxxxxxxx>
Date: Sat, 4 Jun 2005 14:29:39 +0400
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>, James Morris <jmorris@xxxxxxxxxx>, Linux Crypto Mailing List <linux-crypto@xxxxxxxxxxxxxxx>, netdev@xxxxxxxxxxx
In-reply-to: <20050604102204.GA1214@xxxxxxxxxxxxxxxxxxx>
Organization: MIPT
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On Sat, 4 Jun 2005 20:22:04 +1000
Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote:

> On Sat, Jun 04, 2005 at 02:17:31PM +0400, Evgeniy Polyakov wrote:
> >
> > Static scaterlists are not used and new are dinamically allocated.
> 
> That's precisely why we're having this discussion.  We can now
> encrypt/decrypt a 1500 byte packet in 2us so the last thing we
> want is to impose additional latencies on the common case unless
> it's absolutely required.
> 
> If we can shrink the structure used between IPsec and the crypto
> layer then we can allocate the sgbuf off the stack for 99% of
> the users.

I do see that 4 sg are enough for 99% of the users, I event think
2 is enough - it will be 8kb, almost the maximum seen 9kb jumbo frame.
But without sg we sill save 4*sizeof(dma addr) - is it really a price?
For hardware we will need to remap it later...

> Cheers,
> -- 
> Visit Openswan at http://www.openswan.org/
> Email: Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt


        Evgeniy Polyakov

Only failure makes us experts. -- Theo de Raadt

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