Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753802AbaG2P6I (ORCPT ); Tue, 29 Jul 2014 11:58:08 -0400 Received: from sym2.noone.org ([178.63.92.236]:39575 "EHLO sym2.noone.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753672AbaG2P6G (ORCPT ); Tue, 29 Jul 2014 11:58:06 -0400 Date: Tue, 29 Jul 2014 17:58:01 +0200 From: Tobias Klauser To: Thomas Graf Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kaber@trash.net, paulmck@linux.vnet.ibm.com, josh@joshtriplett.org, challa@noironetworks.com, walpole@cs.pdx.edu, dev@openvswitch.org Subject: Re: [PATCH 2/2] netlink: Convert netlink_lookup() to use RCU protected hash table Message-ID: <20140729155801.GB10301@distanz.ch> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Editor: Vi IMproved 7.3 User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014-07-29 at 13:41:33 +0200, Thomas Graf wrote: > Heavy Netlink users such as Open vSwitch spend a considerable amount of > time in netlink_lookup() due to the read-lock on nl_table_lock. Use of > RCU relieves the lock contention. > > Makes use of the new resizable hash table to avoid locking on the > lookup. > > The hash table will grow if entries exceeds 75% of table size up to a > total table size of 64K. It will automatically shrink if usage falls > below 50%. > > Also splits nl_table_lock into a separate spinlock to protect hash table > mutations. This avoids a possible deadlock when the hash table growing > waits on RCU readers to complete via synchronize_rcu() while readers > holding RCU read lock are waiting on the nl_table_lock() to be released > to lock the table for broadcasting. > > Before: > 9.16% kpktgend_0 [openvswitch] [k] masked_flow_lookup > 6.42% kpktgend_0 [pktgen] [k] mod_cur_headers > 6.26% kpktgend_0 [pktgen] [k] pktgen_thread_worker > 6.23% kpktgend_0 [kernel.kallsyms] [k] memset > 4.79% kpktgend_0 [kernel.kallsyms] [k] netlink_lookup > 4.37% kpktgend_0 [kernel.kallsyms] [k] memcpy > 3.60% kpktgend_0 [openvswitch] [k] ovs_flow_extract > 2.69% kpktgend_0 [kernel.kallsyms] [k] jhash2 > > After: > 15.26% kpktgend_0 [openvswitch] [k] masked_flow_lookup > 8.12% kpktgend_0 [pktgen] [k] pktgen_thread_worker > 7.92% kpktgend_0 [pktgen] [k] mod_cur_headers > 5.11% kpktgend_0 [kernel.kallsyms] [k] memset > 4.11% kpktgend_0 [openvswitch] [k] ovs_flow_extract > 4.06% kpktgend_0 [kernel.kallsyms] [k] _raw_spin_lock > 3.90% kpktgend_0 [kernel.kallsyms] [k] jhash2 > [...] > 0.67% kpktgend_0 [kernel.kallsyms] [k] netlink_lookup > > Signed-off-by: Thomas Graf > --- > net/netlink/af_netlink.c | 285 ++++++++++++++++++----------------------------- > net/netlink/af_netlink.h | 18 +-- > net/netlink/diag.c | 11 +- > 3 files changed, 119 insertions(+), 195 deletions(-) > > diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c > index 1b38f7f..7f44468 100644 > --- a/net/netlink/af_netlink.c > +++ b/net/netlink/af_netlink.c [...] > @@ -2996,28 +2939,26 @@ static void *netlink_seq_next(struct seq_file *seq, void *v, loff_t *pos) > > net = seq_file_net(seq); > iter = seq->private; > - s = v; > - do { > - s = sk_next(s); > - } while (s && !nl_table[s->sk_protocol].compare(net, s)); > - if (s) > - return s; > + nlk = v; > + > + rht_for_each_entry_rcu(nlk, nlk->node.next, node) > + if (net_eq(sock_net((struct sock *)nlk), net)) > + return nlk; > > i = iter->link; > j = iter->hash_idx + 1; > > do { > - struct nl_portid_hash *hash = &nl_table[i].hash; > - > - for (; j <= hash->mask; j++) { > - s = sk_head(&hash->table[j]); > + struct rhashtable *ht = &nl_table[i].hash; > + const struct bucket_table *tbl = rht_dereference(ht->tbl, ht); > > - while (s && !nl_table[s->sk_protocol].compare(net, s)) > - s = sk_next(s); > - if (s) { > - iter->link = i; > - iter->hash_idx = j; > - return s; > + for (; j <= tbl->size; j++) { Should the condition j < tbl->size here, since the bucket table only contains `size' buckets? > + rht_for_each_entry_rcu(nlk, tbl->buckets[j], node) { > + if (net_eq(sock_net((struct sock *)nlk), net)) { > + iter->link = i; > + iter->hash_idx = j; > + return nlk; > + } > } > } [...] > diff --git a/net/netlink/diag.c b/net/netlink/diag.c > index 1af29624..7588f34 100644 > --- a/net/netlink/diag.c > +++ b/net/netlink/diag.c [...] > @@ -101,16 +102,20 @@ static int __netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb, > int protocol, int s_num) > { > struct netlink_table *tbl = &nl_table[protocol]; > - struct nl_portid_hash *hash = &tbl->hash; > + struct rhashtable *ht = &tbl->hash; > + const struct bucket_table *htbl = rht_dereference(ht->tbl, ht); > struct net *net = sock_net(skb->sk); > struct netlink_diag_req *req; > + struct netlink_sock *nlsk; > struct sock *sk; > int ret = 0, num = 0, i; > > req = nlmsg_data(cb->nlh); > > - for (i = 0; i <= hash->mask; i++) { > - sk_for_each(sk, &hash->table[i]) { > + for (i = 0; i <= htbl->size; i++) { Same here, condition should be i < htbl->size > + rht_for_each_entry(nlsk, htbl->buckets[i], ht, node) { > + sk = (struct sock *)nlsk; > + > if (!net_eq(sock_net(sk), net)) > continue; > if (num < s_num) { > -- > 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/