netdev - Re: [PATCH net-next 3/3] net: allow to leave the buffer fragmented in skb_cow

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Message-ID: <20131107090135.GA385@gondor.apana.org.au>
Date:	Thu, 7 Nov 2013 17:01:35 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Mathias Krause <mathias.krause@...unet.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	Dmitry Tarnyagin <dmitry.tarnyagin@...kless.no>,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next 3/3] net: allow to leave the buffer fragmented
 in skb_cow_data()

On Thu, Nov 07, 2013 at 09:55:34AM +0100, Mathias Krause wrote:
>
> Indeed. I want to avoid the costly memcpy() on the CPU serving the NIC
> interrupt, as that is a bottleneck in my setup. The packet processing --
> encrypting/decrypting of ESP packets -- gets mostly parallelized via
> pcrypt, so that's fine. But the initial network processing, i.e. getting
> to pcrypt, is what's throttling the throughput currently. (RPS only
> partly solves this problem as for the ESP receive path most traffic ends
> up on the same flow).

How about this: instead of doing in-place encryption/decryption
let's allocate a new destination buffer and encrypt/decrypt into
it.  Then we essentially get the copy for free.

So instead of modifying skb_cow_data you can change esp4.c, etc.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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