On 12/9/20 6:43 PM, Herbert Xu wrote:
On Thu, Dec 10, 2020 at 01:18:12AM +0100, Ard Biesheuvel wrote:
One thing I realized just now is that in the current situation, all
the synchronous skciphers already degrade like this.
I.e., in Ben's case, without the special ccm implementation, ccm(aes)
will resolve to ccm(ctr(aesni),cbcmac(aesni)), which is instantiated
as a sync skcipher using the ctr and ccm/cbcmac templates built on top
of the AES-NI cipher (not skcipher). This cipher will also fall back
to suboptimal scalar code if the SIMD is in use in process context.
Sure, your patch is not making it any worse. But I don't think
the extra code is worth it considering that you're still going to
be running into that slow fallback path all the time.
How can we test this assumption? I see 3x performance gain, so it is not hitting
the fallback path much in my case. What traffic pattern and protocol do you think
will cause the slow fallback path to happen often enough to make this patch not
helpful?
Much better to fix the wireless code to actually go async.
This will not happen any time soon, so better to make incremental
improvement in the crypt code.
Thanks,
Ben
--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc http://www.candelatech.com
