Re: [PATCH 2/3] crypto: algif_akcipher user space interface

On 07/22/2015 11:55 AM, Stephan Mueller wrote:

I concur with you. But we have only two options:

- either use SGLs which the current akcipher API does not do

- or do a memcpy of the sendpage data into the internal buffer

I would memcpy it here. Both the current software and QAT implementations 
do not support SGL so we'll end up memcpy it anyway.
 

As the sendpage already has a speed penalty, I did not like the latter one. 
Based on my measurements for AEAD, Hash and skicpher, sendpage starts to 
become faster than sendmsg with input buffers > 8 to 16 kBytes (sendpage as at 
least 4 syscalls where sendmsg uses only two).

As our current akcipher API does not reach the mentioned limit, I opted to 
require one sendpage call.

But if we change the akcipher API to SGLs, I will lift that limit.

As you said - the preferred way of invoking this would be sendmsg with data instead
of splice. This is only to make splice happy in case the data is not in a contiguous
buffer.
Thanks,
T