netdev - Re: [PATCH RFC] inetpeer: remove AVL implementation in favor of RB tree

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Date:   Wed, 5 Jul 2017 19:38:16 +0300
From:   Mika Penttilä <mika.penttila@...tfour.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>,
        Florian Westphal <fw@...len.de>,
        netfilter-devel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH RFC] inetpeer: remove AVL implementation in favor of RB
 tree

Hi!


On 05.07.2017 19:00, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> As discussed in Faro during Netfilter Workshop 2017, RB trees can be
> used with RCU, using a seqlock.
>
> Note that net/rxrpc/conn_service.c is already using this.
>
> This patch converts inetpeer from AVL tree to RB tree, since it allows
> to remove private AVL code in favor of shared RB code.
>
> $ size net/ipv4/inetpeer.before net/ipv4/inetpeer.after
>    text	   data	    bss	    dec	    hex	filename
>    3195	     40	    128	   3363	    d23	net/ipv4/inetpeer.before
>    1562	     24	      0	   1586	    632	net/ipv4/inetpeer.after
>
> The same technique can be used to speed up
> net/netfilter/nft_set_rbtree.c
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
>  
>  	return p;
> @@ -467,8 +231,9 @@ EXPORT_SYMBOL_GPL(inet_getpeer);
>  void inet_putpeer(struct inet_peer *p)
>  {
>  	p->dtime = (__u32)jiffies;
> -	smp_mb__before_atomic();
> -	refcount_dec(&p->refcnt);
> +
> +	if (refcount_dec_and_test(&p->refcnt))

Missing rb_erase() here...

> +		call_rcu(&p->rcu, inetpeer_free_rcu);
>  }
>  EXPORT_SYMBOL_GPL(inet_putpeer);
>  
>
--Mika