[PATCH] net: compute a more reasonable default ip6_rt_max_size

Arun Sharma
2012-05-25T20:15:34Z

The algorithm is based on ipv4 and alloc_large_system_hash().

The following data is from a x86_64 box I tested:

128MB
$ cat /proc/sys/net/ipv{4,6}/route/max_size
16384
22444

512MB
$ cat /proc/sys/net/ipv{4,6}/route/max_size
65536
99856

1GB
$ cat /proc/sys/net/ipv{4,6}/route/max_size
524288
203068

2GB
$ cat /proc/sys/net/ipv{4,6}/route/max_size
1048576
524288

4GB
$ cat /proc/sys/net/ipv{4,6}/route/max_size
2097152
524288

Signed-off-by: Arun Sharma <asharma@fb.com>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: David Miller <davem@davemloft.net>
---
net/ipv6/route.c | 21 ++++++++++++++++++++-
1 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 49d6ce1..c89ebbb 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2827,6 +2827,16 @@ struct ctl_table * __net_init ipv6_route_sysctl_init(struct net *net)
}
#endif

+static __initdata unsigned long ip6_rt_entries;
+static int __init set_rt_entries(char *str)
+{
+ if (!str)
+ return 0;
+ ip6_rt_entries = simple_strtoul(str, &str, 0);
+ return 1;
+}
+__setup("ip6_rt_entries=", set_rt_entries);
+
static int __net_init ip6_route_net_init(struct net *net)
{
int ret = -ENOMEM;
@@ -2872,8 +2882,17 @@ static int __net_init ip6_route_net_init(struct net *net)
ip6_template_metrics, true);
#endif

+ /* Compute a reasonable default based on what we do for ipv4
+ * total size = 1/16th of total RAM
+ * No more than 512k entries unless overridden on kernel cmdline */
+ if (ip6_rt_entries == 0) {
+ ip6_rt_entries = (totalram_pages << PAGE_SHIFT) >> 4;
+ ip6_rt_entries /= sizeof(struct rt6_info);
+ ip6_rt_entries = min(512 * 1024UL, ip6_rt_entries);
+ }
+
net->ipv6.sysctl.flush_delay = 0;
- net->ipv6.sysctl.ip6_rt_max_size = 4096;
+ net->ipv6.sysctl.ip6_rt_max_size = ip6_rt_entries;
net->ipv6.sysctl.ip6_rt_gc_min_interval = HZ / 2;
net->ipv6.sysctl.ip6_rt_gc_timeout = 60*HZ;
net->ipv6.sysctl.ip6_rt_gc_interval = 30*HZ;
--
1.7.8.4