Re: [dpdk-dev] [PATCH 0/4] DPDK memcpy optimization

[Luke Gorrie <luke@snabb.co>]

Howdy!

This memcpy discussion is absolutely fascinating. Glad to be a fly on the
wall!

On 21 January 2015 at 22:25, Jim Thompson <jim@netgate.com> wrote:

>
> The differences with DPDK are that a) entire cores (including the AVX/SSE
> units and even AES-NI (FPU) are dedicated to DPDK, and b) DPDK is a library,
> and the resulting networking applications are exactly that, applications.
> The "operating system” is now a control plane.
>
>
Here is another thought: when is it time to start thinking of packet copy
as a cheap unit-time operation?

Packets are shrinking exponentially when measured in:

- Cache lines
- Cache load/store operations needed to copy
- Number of vector move instructions needed to copy

because those units are all based on exponentially growing quantities,
while the byte size of packets stays the same for many applications.

So when is it time to stop caring?

(Are we already there, even, for certain conditions? How about Haswell CPU,
data already exclusively in our L1 cache, start and end both known to be
cache-line-aligned?)

Cheers,
-Luke (eagerly awaiting arrival of Haswell server...)