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net/sched: taprio: calculate guard band against actual TC gate close time

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taprio_dequeue_from_txq() looks at the entry->end_time to determine
whether the skb will overrun its traffic class gate, as if at the end of
the schedule entry there surely is a "gate close" event for it. Hint:
maybe there isn't.

For each schedule entry, introduce an array of kernel times which
actually tracks when in the future will there be an *actual* gate close
event for that traffic class, and use that in the guard band overrun
calculation.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vladimir Oltean 2023-02-07 15:54:34 +02:00 committed by David S. Miller
parent d2ad689dec
commit a1e6ad30fa
1 changed files with 34 additions and 6 deletions
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40
net/sched/sch_taprio.c
View file

@ -44,12 +44,12 @@ struct sched_entry {
*/
u64 gate_duration[TC_MAX_QUEUE];
atomic_t budget[TC_MAX_QUEUE];
struct list_head list;
/* The instant that this entry ends and the next one
* should open, the qdisc will make some effort so that no
* packet leaves after this time.
/* The qdisc makes some effort so that no packet leaves
* after this time
*/
ktime_t gate_close_time[TC_MAX_QUEUE];
struct list_head list;
/* Used to calculate when to advance the schedule */
ktime_t end_time;
ktime_t next_txtime;
int index;
@ -148,6 +148,12 @@ static void taprio_calculate_gate_durations(struct taprio_sched *q,
}
}
static bool taprio_entry_allows_tx(ktime_t skb_end_time,
struct sched_entry *entry, int tc)
{
return ktime_before(skb_end_time, entry->gate_close_time[tc]);
}
static ktime_t sched_base_time(const struct sched_gate_list *sched)
{
if (!sched)
@ -644,7 +650,7 @@ static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq,
* guard band ...
*/
if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
ktime_after(guard, entry->end_time))
!taprio_entry_allows_tx(guard, entry, tc))
return NULL;
/* ... and no budget. */
@ -820,10 +826,13 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
{
struct taprio_sched *q = container_of(timer, struct taprio_sched,
advance_timer);
struct net_device *dev = qdisc_dev(q->root);
struct sched_gate_list *oper, *admin;
int num_tc = netdev_get_num_tc(dev);
struct sched_entry *entry, *next;
struct Qdisc *sch = q->root;
ktime_t end_time;
int tc;
spin_lock(&q->current_entry_lock);
entry = rcu_dereference_protected(q->current_entry,
@ -861,6 +870,14 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
end_time = ktime_add_ns(entry->end_time, next->interval);
end_time = min_t(ktime_t, end_time, oper->cycle_end_time);
for (tc = 0; tc < num_tc; tc++) {
if (next->gate_duration[tc] == oper->cycle_time)
next->gate_close_time[tc] = KTIME_MAX;
else
next->gate_close_time[tc] = ktime_add_ns(entry->end_time,
next->gate_duration[tc]);
}
if (should_change_schedules(admin, oper, end_time)) {
/* Set things so the next time this runs, the new
* schedule runs.
@ -1117,8 +1134,11 @@ static int taprio_get_start_time(struct Qdisc *sch,
static void setup_first_end_time(struct taprio_sched *q,
struct sched_gate_list *sched, ktime_t base)
{
struct net_device *dev = qdisc_dev(q->root);
int num_tc = netdev_get_num_tc(dev);
struct sched_entry *first;
ktime_t cycle;
int tc;
first = list_first_entry(&sched->entries,
struct sched_entry, list);
@ -1130,6 +1150,14 @@ static void setup_first_end_time(struct taprio_sched *q,
first->end_time = ktime_add_ns(base, first->interval);
taprio_set_budgets(q, sched, first);
for (tc = 0; tc < num_tc; tc++) {
if (first->gate_duration[tc] == sched->cycle_time)
first->gate_close_time[tc] = KTIME_MAX;
else
first->gate_close_time[tc] = ktime_add_ns(base, first->gate_duration[tc]);
}
rcu_assign_pointer(q->current_entry, NULL);
}