From mboxrd@z Thu Jan  1 00:00:00 1970
From: Florian Westphal <fw@strlen.de>
Subject: Re: [net-next, RFC, 4/8] net: core: add recycle capabilities on skbs
 via page_pool API
Date: Sat, 8 Dec 2018 10:57:58 +0100
Message-ID: <20181208095758.GA32028@strlen.de>
References: <154413874729.21735.10644578158550468689.stgit@firesoul>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
        Toke =?iso-8859-1?Q?H=F8iland-J=F8rgensen?= <toke@toke.dk>,
        ard.biesheuvel@linaro.org, Jason Wang <jasowang@redhat.com>,
        ilias.apalodimas@linaro.org,
        =?iso-8859-1?Q?Bj=F6rnT=F6pel?= <bjorn.topel@intel.com>,
        w@1wt.eu, Saeed Mahameed <saeedm@mellanox.com>,
        mykyta.iziumtsev@gmail.com,
        Daniel Borkmann <borkmann@iogearbox.net>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        Tariq Toukan <tariqt@mellanox.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from Chamillionaire.breakpoint.cc ([146.0.238.67]:51396 "EHLO
        Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK)
        by vger.kernel.org with ESMTP id S1726099AbeLHJ62 (ORCPT
        <rfc822;netdev@vger.kernel.org>); Sat, 8 Dec 2018 04:58:28 -0500
Content-Disposition: inline
In-Reply-To: <154413874729.21735.10644578158550468689.stgit@firesoul>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

Jesper Dangaard Brouer <brouer@redhat.com> wrote:
> 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.