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Message-Id: <20230207135440.1482856-10-vladimir.oltean@nxp.com>
Date: Tue, 7 Feb 2023 15:54:34 +0200
From: Vladimir Oltean <vladimir.oltean@....com>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Jamal Hadi Salim <jhs@...atatu.com>,
Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>,
Vinicius Costa Gomes <vinicius.gomes@...el.com>,
Kurt Kanzenbach <kurt@...utronix.de>,
Jacob Keller <jacob.e.keller@...el.com>,
Gerhard Engleder <gerhard@...leder-embedded.com>,
Jesse Brandeburg <jesse.brandeburg@...el.com>,
Tony Nguyen <anthony.l.nguyen@...el.com>,
intel-wired-lan@...ts.osuosl.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 net-next 09/15] net/sched: taprio: calculate guard band against actual TC gate close time
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@....com>
Reviewed-by: Kurt Kanzenbach <kurt@...utronix.de>
---
v1->v2: rename "tc_gate" to just "gate"
net/sched/sch_taprio.c | 40 ++++++++++++++++++++++++++++++++++------
1 file changed, 34 insertions(+), 6 deletions(-)
diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 08099c1747cc..e625f8f8704f 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -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);
}
--
2.34.1
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