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Date: Fri, 26 Jun 2009 17:54:10 +0200 From: Jarek Poplawski <jarkao2@...il.com> To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.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 08:30:10AM -0700, Paul E. McKenney wrote: > On Fri, Jun 26, 2009 at 05:10:52PM +0200, Jarek Poplawski wrote: > > On Fri, Jun 26, 2009 at 03:52:55PM +0200, Robert Olsson wrote: > > > > > > Jarek Poplawski writes: > > > > > > Thanks, > > > > > > Should be worth testing so we synchronize_rcu instead of doing call_rcu's > > > > > > > Alas take 2 (nor 1) doesn't compile, so here it is again. > > So the idea is to balance memory and latency, so that large changes > (those affecting the root node) get at least one synchronize_rcu(), > while smaller changes just use call_rcu(), correct? This means that > the amount of memory awaiting an RCU grace period is limited, but > the algorithm avoids per-node synchronize_rcu() overhead. > > If I understand the goal correctly, looks good! (Give or take my > limited understanding of fib_trie and is usage, of course.) The goal is practically to replace all call_rcu() during trie_rebalance() with synchronize_rcu() (except some freeing after ENOMEM). I guess currently (<= 2.6.30) call_rcu() can free this memory after trie_rebalance() has finished, that's why there were problems with enabled preemption. So this patch tries to do/force this a bit earlier - at least before the top/largest node is rebalanced. Thanks, Jarek P. > > Thanx, Paul > > > Thanks, > > Jarek P. > > --- (take 3 - for testing) > > > > net/ipv4/fib_trie.c | 30 ++++++++++++++++++++++++------ > > 1 files changed, 24 insertions(+), 6 deletions(-) > > > > diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c > > index 012cf5a..1a4c4b7 100644 > > --- a/net/ipv4/fib_trie.c > > +++ b/net/ipv4/fib_trie.c > > @@ -366,6 +366,17 @@ static void __tnode_vfree(struct work_struct *arg) > > vfree(tn); > > } > > > > +static void __tnode_free(struct tnode *tn) > > +{ > > + size_t size = sizeof(struct tnode) + > > + (sizeof(struct node *) << tn->bits); > > + > > + if (size <= PAGE_SIZE) > > + kfree(tn); > > + else > > + vfree(tn); > > +} > > + > > static void __tnode_free_rcu(struct rcu_head *head) > > { > > struct tnode *tn = container_of(head, struct tnode, rcu); > > @@ -402,7 +413,7 @@ static void tnode_free_flush(void) > > while ((tn = tnode_free_head)) { > > tnode_free_head = tn->tnode_free; > > tn->tnode_free = NULL; > > - tnode_free(tn); > > + __tnode_free(tn); > > } > > } > > > > @@ -1021,18 +1032,25 @@ static void trie_rebalance(struct trie *t, struct tnode *tn) > > (struct node *)tn, wasfull); > > > > tp = node_parent((struct node *) tn); > > - tnode_free_flush(); > > if (!tp) > > break; > > tn = tp; > > } > > > > + if (tnode_free_head) { > > + synchronize_rcu(); > > + tnode_free_flush(); > > + } > > + > > /* Handle last (top) tnode */ > > - if (IS_TNODE(tn)) > > + if (IS_TNODE(tn)) { > > tn = (struct tnode *)resize(t, (struct tnode *)tn); > > - > > - rcu_assign_pointer(t->trie, (struct node *)tn); > > - tnode_free_flush(); > > + rcu_assign_pointer(t->trie, (struct node *)tn); > > + synchronize_rcu(); > > + tnode_free_flush(); > > + } else { > > + rcu_assign_pointer(t->trie, (struct node *)tn); > > + } > > > > return; > > } > > -- > > To unsubscribe from this list: send the line "unsubscribe netdev" in > > the body of a message to majordomo@...r.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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