diff mbox

[stable,3.4,v2,1/2] ipv4: move route garbage collector to work queue

Message ID 547688b69ee9a258cc04e4dad17a90ca6ab182d0.1408045325.git.mleitner@redhat.com
State Not Applicable, archived
Delegated to: David Miller
Headers show

Commit Message

Marcelo Ricardo Leitner Aug. 14, 2014, 7:44 p.m. UTC
Currently the route garbage collector gets called by dst_alloc() if it
have more entries than the threshold. But it's an expensive call, that
don't really need to be done by then.

Another issue with current way is that it allows running the garbage
collector with the same start parameters on multiple CPUs at once, which
is not optimal. A system may even soft lockup if the cache is big enough
as the garbage collectors will be fighting over the hash lock entries.

This patch thus moves the garbage collector to run asynchronously on a
work queue, much similar to how rt_expire_check runs.

There is one condition left that allows multiple executions, which is
handled by the next patch.

Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
---

Notes:
    Hi,
    
    This set is needed for stables <= 3.4, as the IPv4 route cache was
    removed after that.
    
    v1->v2: addressed indentation issue noticed by David Miller
    
    Thanks!

 net/ipv4/route.c | 43 +++++++++++++++++++++++++++++--------------
 1 file changed, 29 insertions(+), 14 deletions(-)

Comments

Marcelo Ricardo Leitner Aug. 19, 2014, 8:31 p.m. UTC | #1
Em 14-08-2014 16:44, Marcelo Ricardo Leitner escreveu:
> Currently the route garbage collector gets called by dst_alloc() if it
> have more entries than the threshold. But it's an expensive call, that
> don't really need to be done by then.
>
> Another issue with current way is that it allows running the garbage
> collector with the same start parameters on multiple CPUs at once, which
> is not optimal. A system may even soft lockup if the cache is big enough
> as the garbage collectors will be fighting over the hash lock entries.
>
> This patch thus moves the garbage collector to run asynchronously on a
> work queue, much similar to how rt_expire_check runs.
>
> There is one condition left that allows multiple executions, which is
> handled by the next patch.
>
> Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> ---
>
> Notes:
>      Hi,
>
>      This set is needed for stables <= 3.4, as the IPv4 route cache was
>      removed after that.
>
>      v1->v2: addressed indentation issue noticed by David Miller
>
>      Thanks!
>

Hi Dave,

Sorry to bother you but WDYT, is this patchset more appropriate?

Thanks,
Marcelo

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David Miller Aug. 19, 2014, 8:34 p.m. UTC | #2
From: Marcelo Ricardo Leitner <mleitner@redhat.com>
Date: Tue, 19 Aug 2014 17:31:50 -0300

> Sorry to bother you but WDYT, is this patchset more appropriate?

Yes it is and it's queued up in patchwork for -stable.
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Marcelo Ricardo Leitner Aug. 19, 2014, 8:38 p.m. UTC | #3
Em 19-08-2014 17:34, David Miller escreveu:
> From: Marcelo Ricardo Leitner <mleitner@redhat.com>
> Date: Tue, 19 Aug 2014 17:31:50 -0300
>
>> Sorry to bother you but WDYT, is this patchset more appropriate?
>
> Yes it is and it's queued up in patchwork for -stable.

Ohh, right, thanks!

Marcelo

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diff mbox

Patch

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 90bc88bbd2a4f73304671e0182df72f450fa901a..9017f2f8aff196b665fc7d4e36116bfda7450011 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -150,6 +150,9 @@  static void		 ipv4_link_failure(struct sk_buff *skb);
 static void		 ip_rt_update_pmtu(struct dst_entry *dst, u32 mtu);
 static int rt_garbage_collect(struct dst_ops *ops);
 
+static void __rt_garbage_collect(struct work_struct *w);
+static DECLARE_WORK(rt_gc_worker, __rt_garbage_collect);
+
 static void ipv4_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
 			    int how)
 {
@@ -977,7 +980,7 @@  static void rt_emergency_hash_rebuild(struct net *net)
    and when load increases it reduces to limit cache size.
  */
 
-static int rt_garbage_collect(struct dst_ops *ops)
+static void __do_rt_garbage_collect(int elasticity, int min_interval)
 {
 	static unsigned long expire = RT_GC_TIMEOUT;
 	static unsigned long last_gc;
@@ -996,7 +999,7 @@  static int rt_garbage_collect(struct dst_ops *ops)
 
 	RT_CACHE_STAT_INC(gc_total);
 
-	if (now - last_gc < ip_rt_gc_min_interval &&
+	if (now - last_gc < min_interval &&
 	    entries < ip_rt_max_size) {
 		RT_CACHE_STAT_INC(gc_ignored);
 		goto out;
@@ -1004,7 +1007,7 @@  static int rt_garbage_collect(struct dst_ops *ops)
 
 	entries = dst_entries_get_slow(&ipv4_dst_ops);
 	/* Calculate number of entries, which we want to expire now. */
-	goal = entries - (ip_rt_gc_elasticity << rt_hash_log);
+	goal = entries - (elasticity << rt_hash_log);
 	if (goal <= 0) {
 		if (equilibrium < ipv4_dst_ops.gc_thresh)
 			equilibrium = ipv4_dst_ops.gc_thresh;
@@ -1021,7 +1024,7 @@  static int rt_garbage_collect(struct dst_ops *ops)
 		equilibrium = entries - goal;
 	}
 
-	if (now - last_gc >= ip_rt_gc_min_interval)
+	if (now - last_gc >= min_interval)
 		last_gc = now;
 
 	if (goal <= 0) {
@@ -1086,15 +1089,33 @@  static int rt_garbage_collect(struct dst_ops *ops)
 	if (net_ratelimit())
 		pr_warn("dst cache overflow\n");
 	RT_CACHE_STAT_INC(gc_dst_overflow);
-	return 1;
+	return;
 
 work_done:
-	expire += ip_rt_gc_min_interval;
+	expire += min_interval;
 	if (expire > ip_rt_gc_timeout ||
 	    dst_entries_get_fast(&ipv4_dst_ops) < ipv4_dst_ops.gc_thresh ||
 	    dst_entries_get_slow(&ipv4_dst_ops) < ipv4_dst_ops.gc_thresh)
 		expire = ip_rt_gc_timeout;
-out:	return 0;
+out:	return;
+}
+
+static void __rt_garbage_collect(struct work_struct *w)
+{
+	__do_rt_garbage_collect(ip_rt_gc_elasticity, ip_rt_gc_min_interval);
+}
+
+static int rt_garbage_collect(struct dst_ops *ops)
+{
+	if (!work_pending(&rt_gc_worker))
+		schedule_work(&rt_gc_worker);
+
+	if (dst_entries_get_fast(&ipv4_dst_ops) >= ip_rt_max_size ||
+	    dst_entries_get_slow(&ipv4_dst_ops) >= ip_rt_max_size) {
+		RT_CACHE_STAT_INC(gc_dst_overflow);
+		return 1;
+	}
+	return 0;
 }
 
 /*
@@ -1288,13 +1309,7 @@  restart:
 			   it is most likely it holds some neighbour records.
 			 */
 			if (attempts-- > 0) {
-				int saved_elasticity = ip_rt_gc_elasticity;
-				int saved_int = ip_rt_gc_min_interval;
-				ip_rt_gc_elasticity	= 1;
-				ip_rt_gc_min_interval	= 0;
-				rt_garbage_collect(&ipv4_dst_ops);
-				ip_rt_gc_min_interval	= saved_int;
-				ip_rt_gc_elasticity	= saved_elasticity;
+				__do_rt_garbage_collect(1, 0);
 				goto restart;
 			}