From 32b293a53deeb220769f9a29357cb151cfb8ee26 Mon Sep 17 00:00:00 2001 From: Josh Hunt Date: Wed, 28 Dec 2011 13:23:07 +0000 Subject: [PATCH] IPv6: Avoid taking write lock for /proc/net/ipv6_route During some debugging I needed to look into how /proc/net/ipv6_route operated and in my digging I found its calling fib6_clean_all() which uses "write_lock_bh(&table->tb6_lock)" before doing the walk of the table. I found this on 2.6.32, but reading the code I believe the same basic idea exists currently. Looking at the rtnetlink code they are only calling "read_lock_bh(&table->tb6_lock);" via fib6_dump_table(). While I realize reading from proc isn't the recommended way of fetching the ipv6 route table; taking a write lock seems unnecessary and would probably cause network performance issues. To verify this I loaded up the ipv6 route table and then ran iperf in 3 cases: * doing nothing * reading ipv6 route table via proc (while :; do cat /proc/net/ipv6_route > /dev/null; done) * reading ipv6 route table via rtnetlink (while :; do ip -6 route show table all > /dev/null; done) * Load the ipv6 route table up with: * for ((i = 0;i < 4000;i++)); do ip route add unreachable 2000::$i; done * iperf commands: * client: iperf -i 1 -V -c * server: iperf -V -s * iperf results - 3 runs each (in Mbits/sec) * nothing: client: 927,927,927 server: 927,927,927 * proc: client: 179,97,96,113 server: 142,112,133 * iproute: client: 928,927,928 server: 927,927,927 lock_stat shows taking the write lock is causing the slowdown. Using this info I decided to write a version of fib6_clean_all() which replaces write_lock_bh(&table->tb6_lock) with read_lock_bh(&table->tb6_lock). With this new function I see the same results as with my rtnetlink iperf test. Signed-off-by: Josh Hunt Signed-off-by: David S. Miller --- include/net/ip6_fib.h | 4 ++++ net/ipv6/ip6_fib.c | 20 ++++++++++++++++++++ net/ipv6/route.c | 2 +- 3 files changed, 25 insertions(+), 1 deletion(-) diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h index 1e8a89f1002a..b26bb8101981 100644 --- a/include/net/ip6_fib.h +++ b/include/net/ip6_fib.h @@ -199,6 +199,10 @@ struct fib6_node *fib6_locate(struct fib6_node *root, const struct in6_addr *daddr, int dst_len, const struct in6_addr *saddr, int src_len); +extern void fib6_clean_all_ro(struct net *net, + int (*func)(struct rt6_info *, void *arg), + int prune, void *arg); + extern void fib6_clean_all(struct net *net, int (*func)(struct rt6_info *, void *arg), int prune, void *arg); diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index 246d8e403f26..b82bcde53f7a 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -1462,6 +1462,26 @@ static void fib6_clean_tree(struct net *net, struct fib6_node *root, fib6_walk(&c.w); } +void fib6_clean_all_ro(struct net *net, int (*func)(struct rt6_info *, void *arg), + int prune, void *arg) +{ + struct fib6_table *table; + struct hlist_node *node; + struct hlist_head *head; + unsigned int h; + + rcu_read_lock(); + for (h = 0; h < FIB6_TABLE_HASHSZ; h++) { + head = &net->ipv6.fib_table_hash[h]; + hlist_for_each_entry_rcu(table, node, head, tb6_hlist) { + read_lock_bh(&table->tb6_lock); + fib6_clean_tree(net, &table->tb6_root, + func, prune, arg); + read_unlock_bh(&table->tb6_lock); + } + } + rcu_read_unlock(); +} void fib6_clean_all(struct net *net, int (*func)(struct rt6_info *, void *arg), int prune, void *arg) { diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 4a62c47599b4..07361dfa8085 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -2680,7 +2680,7 @@ static int rt6_info_route(struct rt6_info *rt, void *p_arg) static int ipv6_route_show(struct seq_file *m, void *v) { struct net *net = (struct net *)m->private; - fib6_clean_all(net, rt6_info_route, 0, m); + fib6_clean_all_ro(net, rt6_info_route, 0, m); return 0; }