RE: [PATCH 0/6] Faster AES-XTS on modern x86_64 CPUs

David Laight
2024-04-03T08:23:02Z

From: Eric Biggers
> Sent: 26 March 2024 16:48
....
> Consider Intel Ice Lake for example, these are the AES-256-XTS encryption speeds
> on 4096-byte messages in MB/s I'm seeing:
>
> xts-aes-aesni 5136
> xts-aes-aesni-avx 5366
> xts-aes-vaes-avx2 9337
> xts-aes-vaes-avx10_256 9876
> xts-aes-vaes-avx10_512 10215
>
> So yes, on that CPU the biggest boost comes just from VAES, staying on AVX2.
> But taking advantage of AVX512 does help a bit more, first from the parts other
> than 512-bit registers, then a bit more from 512-bit registers.

How much does the kernel_fpu_begin() cost on real workloads?
(ie when the registers are live and it forces an extra save/restore)

I've not looked at the code but I often see what looks like
excessive inlining in crypto code.
This will speed up benchmarks but can have a negative effect
on real code both because of the time taken to load the
code and the effect of displacing other code.

It might be that this code is a simple loop....

David

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