netdev - Re: rib_trie / Fix inflate_threshold

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Message-ID: <20090626182143.GN6771@linux.vnet.ibm.com>
Date:	Fri, 26 Jun 2009 11:21:43 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Robert Olsson <robert@...ur.slu.se>,
	Robert Olsson <Robert.Olsson@...a.slu.se>,
	Eric Dumazet <dada1@...mosbay.com>,
	=?ISO-8859-2?Q?Pawe=B3_Staszewski?= 
	<pstaszewski@...are.pl>, Robert Olsson <robert.olsson@....uu.se>,
	Linux Network Development list <netdev@...r.kernel.org>
Subject: Re: rib_trie / Fix inflate_threshold_root. Now=15 size=11 bits

On Fri, Jun 26, 2009 at 08:05:45PM +0200, Jarek Poplawski wrote:
> On Fri, Jun 26, 2009 at 10:05:38AM -0700, Paul E. McKenney wrote:
> ...
> > In that case, simply invoking synchronize_rcu() every once and awhile
> > should take care of things.  This could be at the end of every large
> > trie operation, or you could even count the call_rcu() invocations and
> > do a synchronize_rcu() every 100th, 1,000th, or whatever, based on
> > the amount of memory available.
> 
> OK, for now the minimal change for testing (2.6.30 needs previously
> mentioned two commits from 2.6.31-rc). (I guess I'll send it with a
> changelog after net-next is opened.)

Looks promising to me!!!

							Thanx, Paul

> Thanks,
> Jarek P.
> --- (take 4 - for testing)
> 
>  net/ipv4/fib_trie.c |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index 012cf5a..98b31a1 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
> @@ -1008,7 +1008,7 @@ static void trie_rebalance(struct trie *t, struct tnode *tn)
>  {
>  	int wasfull;
>  	t_key cindex, key;
> -	struct tnode *tp;
> +	struct tnode *tp, *oldtnode = tn;
> 
>  	key = tn->key;
> 
> @@ -1028,8 +1028,12 @@ static void trie_rebalance(struct trie *t, struct tnode *tn)
>  	}
> 
>  	/* Handle last (top) tnode */
> -	if (IS_TNODE(tn))
> +	if (IS_TNODE(tn)) {
> +		/* force memory freeing after last changes */
> +		if (oldtnode != tn)
> +			synchronize_rcu();
>  		tn = (struct tnode *)resize(t, (struct tnode *)tn);
> +	}
> 
>  	rcu_assign_pointer(t->trie, (struct node *)tn);
>  	tnode_free_flush();
--
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