Re: [net-next, RFC, 4/8] net: core: add recycle capabilities on skbs via page_pool API

On 12/08/2018 01:57 AM, Florian Westphal wrote:

Jesper Dangaard Brouer [off-list ref] wrote:

quoted

From: Ilias Apalodimas <ilias.apalodimas@linaro.org>

This patch is changing struct sk_buff, and is thus per-definition
controversial.

Place a new member 'mem_info' of type struct xdp_mem_info, just after
members (flags) head_frag and pfmemalloc, And not in between
headers_start/end to ensure skb_copy() and pskb_copy() work as-is.
Copying mem_info during skb_clone() is required.  This makes sure that
pages are correctly freed or recycled during the altered
skb_free_head() invocation.

I read this to mean that this 'info' isn't accessed/needed until skb
is freed.  Any reason its not added at the end?

This would avoid moving other fields that are probably accessed
more frequently during processing.

But I do not get why the patch is needed.

Adding extra cost for each skb destruction is costly.

I though XDP was all about _not_ having skbs.

Please let's do not slow down the non XDP stack only to make XDP more appealing.