net_sched: sch_fq: account for schedule/timers drifts

[cascardo/linux.git] / net / sched / sch_fq.c

diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index 5dd929c..18e7524 100644 (file)
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -86,6 +86,7 @@ struct fq_sched_data {
 
        struct rb_root  delayed;        /* for rate limited flows */
        u64             time_next_delayed_flow;
+       unsigned long   unthrottle_latency_ns;
 
        struct fq_flow  internal;       /* for non classified or high prio packets */
        u32             quantum;
@@ -408,11 +409,19 @@ static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 
 static void fq_check_throttled(struct fq_sched_data *q, u64 now)
 {
+       unsigned long sample;
        struct rb_node *p;
 
        if (q->time_next_delayed_flow > now)
                return;
 
+       /* Update unthrottle latency EWMA.
+        * This is cheap and can help diagnosing timer/latency problems.
+        */
+       sample = (unsigned long)(now - q->time_next_delayed_flow);
+       q->unthrottle_latency_ns -= q->unthrottle_latency_ns >> 3;
+       q->unthrottle_latency_ns += sample >> 3;
+
        q->time_next_delayed_flow = ~0ULL;
        while ((p = rb_first(&q->delayed)) != NULL) {
                struct fq_flow *f = container_of(p, struct fq_flow, rate_node);
@@ -515,7 +524,12 @@ begin:
                        len = NSEC_PER_SEC;
                        q->stat_pkts_too_long++;
                }
-
+               /* Account for schedule/timers drifts.
+                * f->time_next_packet was set when prior packet was sent,
+                * and current time (@now) can be too late by tens of us.
+                */
+               if (f->time_next_packet)
+                       len -= min(len/2, now - f->time_next_packet);
                f->time_next_packet = now + len;
        }
 out:
@@ -787,6 +801,7 @@ static int fq_init(struct Qdisc *sch, struct nlattr *opt)
        q->initial_quantum      = 10 * psched_mtu(qdisc_dev(sch));
        q->flow_refill_delay    = msecs_to_jiffies(40);
        q->flow_max_rate        = ~0U;
+       q->time_next_delayed_flow = ~0ULL;
        q->rate_enable          = 1;
        q->new_flows.first      = NULL;
        q->old_flows.first      = NULL;
@@ -854,8 +869,8 @@ static int fq_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
        st.flows                  = q->flows;
        st.inactive_flows         = q->inactive_flows;
        st.throttled_flows        = q->throttled_flows;
-       st.pad                    = 0;
-
+       st.unthrottle_latency_ns  = min_t(unsigned long,
+                                         q->unthrottle_latency_ns, ~0U);
        sch_tree_unlock(sch);
 
        return gnet_stats_copy_app(d, &st, sizeof(st));