netdev - Re: [RFC PATCH 4/5] crypto: allow allocation of percpu crypto transforms

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Message-Id: <20081201.042502.223043756.davem@davemloft.net>
Date:	Mon, 01 Dec 2008 04:25:02 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	steffen.klassert@...unet.com, netdev@...r.kernel.org,
	klassert@...hematik.tu-chemnitz.de
Subject: Re: [RFC PATCH 4/5] crypto: allow allocation of percpu crypto
 transforms

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Mon, 1 Dec 2008 19:38:28 +0800

> On Mon, Dec 01, 2008 at 08:19:43AM +0100, Steffen Klassert wrote:
> > From: Steffen Klassert <steffen.klassert@...unet.com>
> > 
> > This patch adds functions to alloc/free crypto transforms
> > as percpu data.
> > 
> > Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
> 
> I'd prefer to just have the user call crypto_alloc_tfm for each
> CPU.  This is the slow path after all so we don't need to optimise
> it that much.

I somewhat disagree.

If you make this num_cpus expensive, I can nearly guarentee you this
will show up in the profiles for the workloads I was using to test the
control path optimizations with all the dynamic hash tables and
streamlined lookups.

Some cell phones networks, I am to understand, can allocate 6 SAs when
they come onto the network, perhaps never use them, then go away.
Multiply that by the number of cell phones using a network in a busy
downtown area of a city and it could be very interesting.

If, in those changes, I was removing atomics to make rule insert and
delete faster, making more TFM allocs happen might be a big no-no :)
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