linux-kernel - Re: [PATCH] Using Intel CRC32 instruction to accelerate CRC32c algorithm by new crypto API.

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Date:	Mon, 04 Aug 2008 09:45:37 -0400
From:	Chris Mason <chris.mason@...cle.com>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	Austin Zhang <austin_zhang@...ux.intel.com>,
	herbert@...dor.apana.org.au, davem@...emloft.net,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: Re: [PATCH] Using Intel CRC32 instruction to accelerate CRC32c
	algorithm by new crypto API.

On Mon, 2008-08-04 at 11:45 +0100, David Woodhouse wrote:
> On Mon, 2008-08-04 at 06:35 -0400, Austin Zhang wrote:
> > On Mon, 2008-08-04 at 11:12 +0100, David Woodhouse wrote:
> > > You could perhaps just use 'unsigned long' here, to avoid the ifdef.
> > Thanks. 
> > > And it would be nice if we could make libcrc32c use this too, rather
> > > than just the 'crypto' users.
> > From previous discussing, herbert would like to transfer the libcrc32c 
> > interface by new crypto because there were few user using the current 
> > libcrc32c interface. 
> 
> Are we deprecating libcrc32c, then? Or just turning it into a wrapper
> around the crypto code?
> 

Long term I'd like to switch btrfs to the crypto api, but right now I'm
using libcrc32c.

>>From a performance point of view I'm probably reading the crypto API
code wrong, but it looks like my choices are to either have a long
standing context and use locking around the digest/hash calls to protect
internal crypto state, or create a new context every time and take a
perf hit while crypto looks up the right module.

Either way it looks slower than just calling good old libcrc32c.

-chris

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