[dm-devel] [PATCH] DM-CRYPT: Scale to multiple CPUs
Herbert Xu
herbert at gondor.hengli.com.au
Wed Jun 2 05:14:03 UTC 2010
On Wed, Jun 02, 2010 at 01:10:00AM -0400, Mikulas Patocka wrote:
>
> And how can I use pcrypt for dm-crypt? After a quick look at pcrypt
> sources, it seems to be dependent on aead and not useable for general
> encryption algorithms at all.
You instantiate a pcrypt variant of whatever algorithm that you're
using. For example, if you're using XTS then you should instantiate
pcrypt(xts(aes)). Currently you must use tcrypt to instantiate.
> I tried cryptd --- in theory it should work by requesting the algorithm
> like cryptd(cbc(aes)) --- but if I replace "%s(%s)" with "cryptd(%s(%s))"
> in dm-crypt sources it locks up and doesn't work.
cryptd is something else altogether. However, it certainly should
not lock up. What kernel version is this?
> > This would be inappropriate for upper layer code as they do not
> > know whether the underlying algorithm should be parallelised,
> > e.g., a PCI offload board certainly should not be parallelised.
>
> The upper layer should ideally request "cbc(aes)" and the crypto routine
> should select the most efficient implementation --- sync on single-core
> system, async with cryptd on multi-core system and async with hardware
> implementation if you have HIFN crypto card.
That's exactly what will happen when the admin instantiates pcrypt.
dm-crypt simply needs to specify cbc(aes) and it will get pcrypt
automatically.
The point is that on a modern processor like Nehalem you don't need
pcrypt.
> It is pointless to track the submitting CPU.
No you are wrong.
Cheers,
--
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