Re: [PATCH v5 0/3] Recycle buffers from Tx to Rx

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 30 Mar 2023 14:29:36 +0800
Feifei Wang <feifei.wang2@arm.com> wrote:

> Currently, the transmit side frees the buffers into the lcore cache and
> the receive side allocates buffers from the lcore cache. The transmit
> side typically frees 32 buffers resulting in 32*8=256B of stores to
> lcore cache. The receive side allocates 32 buffers and stores them in
> the receive side software ring, resulting in 32*8=256B of stores and
> 256B of load from the lcore cache.
> 
> This patch proposes a mechanism to avoid freeing to/allocating from
> the lcore cache. i.e. the receive side will free the buffers from
> transmit side directly into its software ring. This will avoid the 256B
> of loads and stores introduced by the lcore cache. It also frees up the
> cache lines used by the lcore cache. And we can call this mode as buffer
> recycle mode.


My naive reading of this is that lcore cache update is slow on ARM
so you are introducing yet another cache. Perhaps a better solution
would be to figure out/optimize the lcore cache to work better.

Adding another layer of abstraction is not going to help everyone
and the implementation you chose requires modifications to drivers
to get it to work.

In current form, this is not acceptable.