Re: [PATCH v2 0/2] Implement AES on ARM using x86 instructions and vv

[Richard Henderson <richard.henderson@linaro.org>]

On 5/31/23 10:08, Richard Henderson wrote:
> On 5/31/23 09:47, Ard Biesheuvel wrote:
>> On Wed, 31 May 2023 at 18:33, Richard Henderson
>>> Thanks.  I spent some time yesterday looking at this, with an encrypted disk test case and
>>> could only measure 0.6% and 0.5% for total overhead of decrypt and encrypt respectively.
>>>
>>
>> I don't understand what 'overhead' means in this context. Are you
>> saying you saw barely any improvement?
> 
> I saw, without changes, just over 1% of total system emulation time was devoted to aes, 
> which gives an upper limit to the runtime improvement possible there.  But I'll have a 
> look at tcrypt.

Using

# insmod /lib/modules/5.10.0-21-arm64/kernel/crypto/tcrypt.ko mode=600 sec=10

I see

   25.50%  qemu-system-aar  qemu-system-aarch64      [.] helper_crypto_aese
   25.36%  qemu-system-aar  qemu-system-aarch64      [.] helper_crypto_aesmc
    6.66%  qemu-system-aar  qemu-system-aarch64      [.] rebuild_hflags_a64
    3.25%  qemu-system-aar  qemu-system-aarch64      [.] tb_lookup
    2.52%  qemu-system-aar  qemu-system-aarch64      [.] fp_exception_el
    2.35%  qemu-system-aar  qemu-system-aarch64      [.] helper_lookup_tb_ptr

Obviously a crypto-heavy test, but 51% of runtime is certainly worth more work.


r~