netdev - Re: [PATCH net-2.6] Re: rib_trie / Fix inflate_threshold

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Message-ID: <20090705213232.GG8943@linux.vnet.ibm.com>
Date:	Sun, 5 Jul 2009 14:32:32 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Paweł Staszewski <pstaszewski@...are.pl>,
	Linux Network Development list <netdev@...r.kernel.org>,
	Robert Olsson <robert@...ur.slu.se>
Subject: Re: [PATCH net-2.6] Re: rib_trie / Fix inflate_threshold_root.
	Now=15 size=11 bits

On Sun, Jul 05, 2009 at 07:32:08PM +0200, Jarek Poplawski wrote:
> On Sun, Jul 05, 2009 at 06:20:03PM +0200, Jarek Poplawski wrote:
> > On Sun, Jul 05, 2009 at 02:30:03AM +0200, Paweł Staszewski wrote:
> > > Oh
> > >
> > > I forgot - please Jarek give me patch with sync rcu and i will make test  
> > > on preempt kernel
> > 
> > Probably non-preempt kernel might need something like this more, but
> > comparing is always interesting. This patch is based on Paul's
> > suggestion (I hope).
> 
> Hold on ;-) Here is something even better... Syncing after 128 pages
> might be still too slow, so here is a higher initial value, 1000, plus
> you can change this while testing in:
> 
> /sys/module/fib_trie/parameters/sync_pages
> 
> It would be interesting to find the lowest acceptable value.

Looks like a promising approach to me!

							Thanx, Paul

> Jarek P.
> ---> (synchronize take 8; apply on top of the 2.6.29.x with the last
>  	all-in-one patch, or net-2.6)
> 
>  net/ipv4/fib_trie.c |   12 ++++++++++++
>  1 files changed, 12 insertions(+), 0 deletions(-)
> 
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index 00a54b2..decc8d0 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
> @@ -71,6 +71,7 @@
>  #include <linux/netlink.h>
>  #include <linux/init.h>
>  #include <linux/list.h>
> +#include <linux/moduleparam.h>
>  #include <net/net_namespace.h>
>  #include <net/ip.h>
>  #include <net/protocol.h>
> @@ -164,6 +165,10 @@ static struct tnode *inflate(struct trie *t, struct tnode *tn);
>  static struct tnode *halve(struct trie *t, struct tnode *tn);
>  /* tnodes to free after resize(); protected by RTNL */
>  static struct tnode *tnode_free_head;
> +static size_t tnode_free_size;
> +
> +static int sync_pages __read_mostly = 1000;
> +module_param(sync_pages, int, 0640);
> 
>  static struct kmem_cache *fn_alias_kmem __read_mostly;
>  static struct kmem_cache *trie_leaf_kmem __read_mostly;
> @@ -393,6 +398,8 @@ static void tnode_free_safe(struct tnode *tn)
>  	BUG_ON(IS_LEAF(tn));
>  	tn->tnode_free = tnode_free_head;
>  	tnode_free_head = tn;
> +	tnode_free_size += sizeof(struct tnode) +
> +			   (sizeof(struct node *) << tn->bits);
>  }
> 
>  static void tnode_free_flush(void)
> @@ -404,6 +411,11 @@ static void tnode_free_flush(void)
>  		tn->tnode_free = NULL;
>  		tnode_free(tn);
>  	}
> +
> +	if (tnode_free_size >= PAGE_SIZE * sync_pages) {
> +		tnode_free_size = 0;
> +		synchronize_rcu();
> +	}
>  }
> 
>  static struct leaf *leaf_new(void)
> --
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