netdev - Re: [PATCH 16/40] netvm: hook skb allocation to reserves

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Message-ID: <39e6f6c70705040707l4556347akb5d5d8fe9282c041@mail.gmail.com>
Date:	Fri, 4 May 2007 11:07:12 -0300
From:	"Arnaldo Carvalho de Melo" <acme@...stprotocols.net>
To:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	netdev@...r.kernel.org,
	"Trond Myklebust" <trond.myklebust@....uio.no>,
	"Thomas Graf" <tgraf@...g.ch>,
	"David Miller" <davem@...emloft.net>,
	"James Bottomley" <James.Bottomley@...eleye.com>,
	"Mike Christie" <michaelc@...wisc.edu>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Daniel Phillips" <phillips@...gle.com>
Subject: Re: [PATCH 16/40] netvm: hook skb allocation to reserves

On 5/4/07, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> Change the skb allocation api to indicate RX usage and use this to fall back to
> the reserve when needed. Skbs allocated from the reserve are tagged in
> skb->emergency.
>
> Teach all other skb ops about emergency skbs and the reserve accounting.
>
> Use the (new) packet split API to allocate and track fragment pages from the
> emergency reserve. Do this using an atomic counter in page->index. This is
> needed because the fragments have a different sharing semantic than that
> indicated by skb_shinfo()->dataref.
>
> (NOTE the extra atomic overhead is only for those pages allocated from the
> reserves - it does not affect the normal fast path.)
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  include/linux/skbuff.h |   22 +++++-
>  net/core/skbuff.c      |  161 ++++++++++++++++++++++++++++++++++++++++++-------
>  2 files changed, 157 insertions(+), 26 deletions(-)

>
> +#define skb_alloc_rx(skb) (skb_emergency(skb) ? SKB_ALLOC_RX : 0)

skb_alloc_rx seems to imply "alloc an skb for rx", not "gimme the
right flags to allocate a skb for rx". Can this be changed to
"skb_alloc_rx_flag(skb)", similar to the existing sock_flag() for
socks?

- Arnaldo
-
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