net_sched: gen_estimator: complete rewrite of rate estimators

1) Old code was hard to maintain, due to complex lock chains.
   (We probably will be able to remove some kfree_rcu() in callers)

2) Using a single timer to update all estimators does not scale.

3) Code was buggy on 32bit kernel (WRITE_ONCE() on 64bit quantity
   is not supposed to work well)

In this rewrite :

- I removed the RB tree that had to be scanned in
  gen_estimator_active(). qdisc dumps should be much faster.

- Each estimator has its own timer.

- Estimations are maintained in net_rate_estimator structure,
  instead of dirtying the qdisc. Minor, but part of the simplification.

- Reading the estimator uses RCU and a seqcount to provide proper
  support for 32bit kernels.

- We reduce memory need when estimators are not used, since
  we store a pointer, instead of the bytes/packets counters.

- xt_rateest_mt() no longer has to grab a spinlock.
  (In the future, xt_rateest_tg() could be switched to per cpu counters)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 6 deletions

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index f893d180da1c..2095c83ce773 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -41,8 +41,7 @@ static void tcf_hash_destroy(struct tcf_hashinfo *hinfo, struct tc_action *p)
 	spin_lock_bh(&hinfo->lock);
 	hlist_del(&p->tcfa_head);
 	spin_unlock_bh(&hinfo->lock);
-	gen_kill_estimator(&p->tcfa_bstats,
-			   &p->tcfa_rate_est);
+	gen_kill_estimator(&p->tcfa_rate_est);
 	/*
 	 * gen_estimator est_timer() might access p->tcfa_lock
 	 * or bstats, wait a RCU grace period before freeing p
@@ -237,8 +236,7 @@ EXPORT_SYMBOL(tcf_hash_check);
 void tcf_hash_cleanup(struct tc_action *a, struct nlattr *est)
 {
 	if (est)
-		gen_kill_estimator(&a->tcfa_bstats,
-				   &a->tcfa_rate_est);
+		gen_kill_estimator(&a->tcfa_rate_est);
 	call_rcu(&a->tcfa_rcu, free_tcf);
 }
 EXPORT_SYMBOL(tcf_hash_cleanup);
@@ -670,8 +668,7 @@ int tcf_action_copy_stats(struct sk_buff *skb, struct tc_action *p,
 		goto errout;
 
 	if (gnet_stats_copy_basic(NULL, &d, p->cpu_bstats, &p->tcfa_bstats) < 0 ||
-	    gnet_stats_copy_rate_est(&d, &p->tcfa_bstats,
-				     &p->tcfa_rate_est) < 0 ||
+	    gnet_stats_copy_rate_est(&d, &p->tcfa_rate_est) < 0 ||
 	    gnet_stats_copy_queue(&d, p->cpu_qstats,
 				  &p->tcfa_qstats,
 				  p->tcfa_qstats.qlen) < 0)