Atom C2758 - loading aesni(4) reduces performance

[Christoph Moench-Tegeder]

## Kevin Day (toasty at dragondata.com):

> > If you have cryptodev loaded, this is to be expected as OpenSSL will
> > use /dev/crypto instead of the AES-NI instructions..  Just don't load
> > cryptodev and you'll be fine..
> 
> So to make sure I’m understanding… openssl has native AES-NI support, and
> it also can use /dev/crypto. It’s preferring /dev/crypto, but /dev/crypto
> has much higher overhead?

Yes (I hadn't thought of cryptodev, because "why would one load that
without really special crypto hardware?").
The overhead is obvious - when offloading the crypto operations to
the kernel, the benefit of the kernel/hardware crypto support has
to be better than the penalty of communicating with the kernel; and
as you already have AES-NI support in openssl, there's not that much
chance that the kernel is that much faster than openssl itself.

Regards,
Christoph

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