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

[Tadeusz Struk <tadeusz.struk@intel.com>]

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