Re: [PATCH 0/2] add AES-NI/AVX2/x86_64 implementation

[Tianjia Zhang]

Hi David,

On 8/20/21 6:03 PM, David Laight wrote:
> From: Tianjia Zhang
> > Sent: 18 August 2021 04:31
> >
> > This patchsets exported some of the common functions implemented by
> > the SM4 AESNI/AVX algorithm, and reused these functions to achieve
> > the acceleration of AESNI/AVX2 implementation.
>
> These functions need bracketing by kernel_fpu_enable()
> (or whatever it is called.)
> That will significantly affect the performance.
>
> Also the functions look pretty big (I don't know how big
> the generic ones are) and will take time to load into the I$
> and will displace other code.
>
> So while a hot-cache benchmark might show improvements
> for repeated calls is isn't obvious that any significant
> gain will be made for real-life calls which could easily
> be of single buffers.
>
> 	David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)

Yes, the functions bracketed by kernel_fpu_begin() do affect 
performance. It seems that the kernel can only do this, so by processing 
as much data as possible in a kernel_fpu_begin/end() operation to 
improve performance. actually do it now.

Best regards,
Tianjia