From c9503e0fe052020e0294cd07d0ecd982eb7c9177 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Mon, 27 Apr 2009 05:42:24 -0700 Subject: [PATCH] ipv4: Limit size of route cache hash table Right now we have no upper limit on the size of the route cache hash table. On a 128GB POWER6 box it ends up as 32MB: IP route cache hash table entries: 4194304 (order: 9, 33554432 bytes) It would be nice to cap this for memory consumption reasons, but a massive hashtable also causes a significant spike when measuring OS jitter. With a 32MB hashtable and 4 million entries, rt_worker_func is taking 5 ms to complete. On another system with more memory it's taking 14 ms. Even though rt_worker_func does call cond_sched() to limit its impact, in an HPC environment we want to keep all sources of OS jitter to a minimum. With the patch applied we limit the number of entries to 512k which can still be overriden by using the rt_entries boot option: IP route cache hash table entries: 524288 (order: 6, 4194304 bytes) With this patch rt_worker_func now takes 0.460 ms on the same system. Signed-off-by: Anton Blanchard Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/route.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index c40debe..c4c60e9 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -3397,7 +3397,7 @@ int __init ip_rt_init(void) 0, &rt_hash_log, &rt_hash_mask, - 0); + rhash_entries ? 0 : 512 * 1024); memset(rt_hash_table, 0, (rt_hash_mask + 1) * sizeof(struct rt_hash_bucket)); rt_hash_lock_init(); -- 1.8.2.3