netdev - Re: [PATCH -next 3/4] sched: remove qdisc_rehape

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Message-ID: <1465407776.7945.24.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Wed, 08 Jun 2016 10:42:56 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Florian Westphal <fw@...len.de>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH -next 3/4] sched: remove qdisc_rehape_fail

On Wed, 2016-06-08 at 17:35 +0200, Florian Westphal wrote:
> After the removal of TCA_CBQ_POLICE in cbq scheduler qdisc->reshape_fail
> is always NULL, i.e. qdisc_rehape_fail is now the same as qdisc_drop.
> 
> Signed-off-by: Florian Westphal <fw@...len.de>
> ---
>  include/net/sch_generic.h | 19 -------------------
>  net/sched/sch_fifo.c      |  4 ++--
>  net/sched/sch_netem.c     |  4 ++--
>  net/sched/sch_plug.c      |  2 +-
>  net/sched/sch_tbf.c       |  4 ++--
>  5 files changed, 7 insertions(+), 26 deletions(-)
> 
> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> index c069ac1..a9aec63 100644
> --- a/include/net/sch_generic.h
> +++ b/include/net/sch_generic.h
> @@ -63,9 +63,6 @@ struct Qdisc {
>  	struct list_head	list;
>  	u32			handle;
>  	u32			parent;
> -	int			(*reshape_fail)(struct sk_buff *skb,
> -					struct Qdisc *q);
> -
>  	void			*u32_node;
>  

You removed 2 pointers from Qdisc, so now next_sched & gso_skb are in a
different cache line than ->state

Some performance penalty is expected, unless you move a read_mostly
field there to compensate.