[RFC v2] non-temporal memcpy

[David Christensen]

On 7/19/22 8:26 AM, Morten Brørup wrote:
> This RFC proposes a set of functions optimized for non-temporal memory copy.
> 
> At this stage, I am asking for feedback on the concept.
> 
> Applications sometimes data to another memory location, which is only used
> much later.
> In this case, it is inefficient to pollute the data cache with the copied
> data.
> 
> An example use case (originating from a real life application):
> Copying filtered packets, or the first part of them, into a capture buffer
> for offline analysis.
> 
> The purpose of these functions is to achieve a performance gain by not
> polluting the cache when copying data.
> Although the throughput may be improved by further optimization, I do not
> consider througput optimization relevant initially.
> 
Assume that fallback to the standard temporal memcpy is an acceptable 
implementation when not supported by the architecture, yes?  My internal 
queries on the POWER side indicate that there's no support in P8/P9/P10 
ISA for such functionality.

Dave