On Fri, Jul 10, 2009 at 04:47:54PM +0200, Jarek Poplawski wrote:

On Fri, Jul 10, 2009 at 01:59:00AM +0200, Paweł Staszewski wrote:

quoted

Today i make other tests with change of  
/proc/sys/net/ipv4/rt_cache_rebuild_count and kernel 2.6.30.1

And when rt_cache_rebuild_count is set to "-1" i have always load on  
x86_64 machine approx 40-50% of each cpu where network card is binded by  
irq_aff

when rt_cache_rebuild_count is set to more than "-1" i have 15 to 20 sec  
of 1 to 3% cpu and after 40-50% cpu

...

Here is one more patch for testing (with caution!). It adds possibility
to turn off cache disabling (so it should even more resemble 2.6.28)
after setting: rt_cache_rebuild_count = 0

I'd like you to try this patch:
1) together with the previous patch and "rt_cache_rebuild_count = 0"
   to check if there is still the difference wrt. 2.6.28; Btw., let
   me know which /proc/sys/net/ipv4/route/* settings do you need to
   change and why

2) alone (without the previous patch) and "rt_cache_rebuild_count = 0"

3) if it's possible to try 2.6.30.1 without these patches, but with
   default /proc/sys/net/ipv4/route/* settings, and higher
   rt_cache_rebuild_count, e.g. 100; I'm interested if/how long it
   takes to trigger higher cpu load and the warning "... rebuilds is
   over limit, route caching disabled"; (Btw., I wonder why you didn't
   mention about these or maybe also other route caching warnings?)

Here is take 2 to respect setting "rt_cache_rebuild_count = 0" even
after cache rebuild counter has been increased earlier. (Btw, don't
forget about this setting after going back to vanilla kernel.)

Jarek P.

--- (debugging patch #2 take 2; apply to 2.6.30.1 or 2.6.29.6)


 net/ipv4/route.c |   21 ++++++++++++++-------
 1 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 278f46f..f74db20 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c

@@ -678,8 +678,9 @@ static inline u32 rt_score(struct rtable *rt)
 
 static inline bool rt_caching(const struct net *net)
 {
-	return net->ipv4.current_rt_cache_rebuild_count <=
-		net->ipv4.sysctl_rt_cache_rebuild_count;
+	return (net->ipv4.current_rt_cache_rebuild_count <=
+		net->ipv4.sysctl_rt_cache_rebuild_count) ||
+	       net->ipv4.sysctl_rt_cache_rebuild_count == 0;
 }
 
 static inline bool compare_hash_inputs(const struct flowi *fl1,

@@ -1181,12 +1182,18 @@ restart:
 	} else {
 		if (chain_length > rt_chain_length_max) {
 			struct net *net = dev_net(rt->u.dst.dev);
-			int num = ++net->ipv4.current_rt_cache_rebuild_count;
-			if (!rt_caching(dev_net(rt->u.dst.dev))) {
-				printk(KERN_WARNING "%s: %d rebuilds is over limit, route caching disabled\n",
-					rt->u.dst.dev->name, num);
+
+			if (net->ipv4.sysctl_rt_cache_rebuild_count > 0) {
+				int num = ++net->ipv4.current_rt_cache_rebuild_count;
+
+				if (!rt_caching(net))
+					printk(KERN_WARNING
+					       "%s: %d rebuilds is over limit, "
+					       "route caching disabled\n",
+					       rt->u.dst.dev->name, num);
+
+				rt_emergency_hash_rebuild(net);
 			}
-			rt_emergency_hash_rebuild(dev_net(rt->u.dst.dev));
 		}
 	}