netdev - [question] why 'struct skb_shared_info->frags' use page idea insdead direct memory pointer?

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Message-ID: <CAHt-b_OiPm-41A8eLZO6UQUmLSbdMZpduVG53ArGhQQcmwDjxA@mail.gmail.com>
Date: Sun, 14 Apr 2024 10:13:21 +0800
From: 刘立超 <liulichao09679@...il.com>
To: netdev@...r.kernel.org
Subject: [question] why 'struct skb_shared_info->frags' use page idea insdead
 direct memory pointer?

I have encountered a question about how gro combine skbs, simply say,
there are two ways:
1. use 'skb->shinfo->frags'
2. use 'skb->shinfo->frag_list'

I have two questions:
1. why 'skb->shinfo->frags' use page idea, what's the advantage over
memory pointer?
2. from history patch "d3836f21b0af5513ef55701dd3f50b8c42e44c7a", I
can get 'skb->shinfo->frags' is better than 'skb->shinfo->frag_list'.
but i don't know why.
    the patch say:"gro uses the frag_list fallback, very inefficient
since we keep all struct sk_buff around", but if 'skb->shinfo->frags'
use memory pointer, we can free skb struct immediately.

Maybe it's a simple question. Thank you.