Re: [PATCH 0/4] crypto: introduce generic dynamic software fallback and EIP93 support

[Jihong Min]

Hi,

On 8/10/26 16:55, Herbert Xu wrote:
> On Tue, Jul 28, 2026 at 05:43:28PM +0900, Jihong Min wrote:
>>
>> The tcrypt AES-128-CBC results are median cycles from five runs. Lower
>> is better. Disabled uses cbc(aes-eip93) directly, while enabled uses
>> fallback(cbc(aes-eip93)).
>>
>>   Request   Disabled   Enabled   Cycle reduction
>>    (bytes)   (cycles)  (cycles)
>>        16        322        18             94.4%
>>        64        274        43             84.3%
>>       128        292        74             74.7%
>>       256        312       138             55.8%
>>      1024        434       439             -1.2%
>>      1424        492       488              0.8%
>>      4096        980      1023             -4.4%
> 
> Do these results vary that much at run-time that requires a run-time
> test? Surely you can predict the outcome for the platforms involved?>
> It appears to me that you're simply adding complexity for something
> that can already be easily tuned by the administrator through the
> algorithm priorities.

Many crypto IP including EIP93 can have different host CPU performance.
This idea is directly from in-kernel raid6 module to dynamically
calculate this host CPU performance to set the boundaries.

> 
> In fact, why not implement the benchmark in user-space and then based
> on that result adjust the priorities?

The same reason why there is the kernel crypto API. It is a single point
(both AF_ALG and devcrypto) of entrance to each crypto device
implementation. It is best to control within them.

> 
> Cheers,


Sincerely,
Jihong Min