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author | Josh Hunt <joshhunt00@gmail.com> | 2011-12-28 13:23:07 +0000 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2011-12-30 17:07:33 -0500 |
commit | 32b293a53deeb220769f9a29357cb151cfb8ee26 (patch) | |
tree | 449cac8df3c48be49657331c9b6958ccdd360e18 /net/ipv6 | |
parent | c9da99e6475f92653139e43f3c30c0cd011a0fd8 (diff) | |
download | linux-stable-32b293a53deeb220769f9a29357cb151cfb8ee26.tar.gz linux-stable-32b293a53deeb220769f9a29357cb151cfb8ee26.tar.bz2 linux-stable-32b293a53deeb220769f9a29357cb151cfb8ee26.zip |
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 <ipv6 addr>
* 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 <joshhunt00@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6')
-rw-r--r-- | net/ipv6/ip6_fib.c | 20 | ||||
-rw-r--r-- | net/ipv6/route.c | 2 |
2 files changed, 21 insertions, 1 deletions
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; } |