[PATCH 5/7] Traffic control using high-resolution timer issue

Erez Geva
2020-10-01T21:03:16Z

- Add new schedule function for Qdisc watchdog.
The function avoids reprogram if watchdog already expire
before new expire.

- Use new schedule function in ETF.

- Add ETF range value to kernel configuration.
as the value is characteristic to Hardware.

Signed-off-by: Erez Geva <erez.geva.ext@siemens.com>
---
include/net/pkt_sched.h | 2 ++
net/sched/Kconfig | 8 ++++++++
net/sched/sch_api.c | 33 +++++++++++++++++++++++++++++++++
net/sched/sch_etf.c | 10 ++++++++--
4 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index ac8c890a2657..4306c2773778 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -78,6 +78,8 @@ void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc);

void qdisc_watchdog_schedule_range_ns(struct qdisc_watchdog *wd, u64 expires,
u64 delta_ns);
+void qdisc_watchdog_schedule_soon_ns(struct qdisc_watchdog *wd, u64 expires,
+ u64 delta_ns);

static inline void qdisc_watchdog_schedule_ns(struct qdisc_watchdog *wd,
u64 expires)
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index a3b37d88800e..0f5261ee9e1b 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -195,6 +195,14 @@ config NET_SCH_ETF
To compile this code as a module, choose M here: the
module will be called sch_etf.

+config NET_SCH_ETF_TIMER_RANGE
+ int "ETF Watchdog time range delta in nano seconds"
+ depends on NET_SCH_ETF
+ default 5000
+ help
+ Specify the time range delta for ETF watchdog
+ Default is 5 microsecond
+
config NET_SCH_TAPRIO
tristate "Time Aware Priority (taprio) Scheduler"
help
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index ebf59ca1faab..80bd09555f5e 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -645,6 +645,39 @@ void qdisc_watchdog_schedule_range_ns(struct qdisc_watchdog *wd, u64 expires,
}
EXPORT_SYMBOL(qdisc_watchdog_schedule_range_ns);

+void qdisc_watchdog_schedule_soon_ns(struct qdisc_watchdog *wd, u64 expires,
+ u64 delta_ns)
+{
+ if (test_bit(__QDISC_STATE_DEACTIVATED,
+ &qdisc_root_sleeping(wd->qdisc)->state))
+ return;
+
+ if (wd->last_expires == expires)
+ return;
+
+ /**
+ * If expires is in [0, now + delta_ns],
+ * do not program it.
+ */
+ if (expires <= ktime_to_ns(hrtimer_cb_get_time(&wd->timer)) + delta_ns)
+ return;
+
+ /**
+ * If timer is already set in [0, expires + delta_ns],
+ * do not reprogram it.
+ */
+ if (hrtimer_is_queued(&wd->timer) &&
+ wd->last_expires <= expires + delta_ns)
+ return;
+
+ wd->last_expires = expires;
+ hrtimer_start_range_ns(&wd->timer,
+ ns_to_ktime(expires),
+ delta_ns,
+ HRTIMER_MODE_ABS_PINNED);
+}
+EXPORT_SYMBOL(qdisc_watchdog_schedule_soon_ns);
+
void qdisc_watchdog_cancel(struct qdisc_watchdog *wd)
{
hrtimer_cancel(&wd->timer);
diff --git a/net/sched/sch_etf.c b/net/sched/sch_etf.c
index c48f91075b5c..48b2868c4672 100644
--- a/net/sched/sch_etf.c
+++ b/net/sched/sch_etf.c
@@ -20,6 +20,11 @@
#include <net/pkt_sched.h>
#include <net/sock.h>

+#ifdef CONFIG_NET_SCH_ETF_TIMER_RANGE
+#define NET_SCH_ETF_TIMER_RANGE CONFIG_NET_SCH_ETF_TIMER_RANGE
+#else
+#define NET_SCH_ETF_TIMER_RANGE (5 * NSEC_PER_USEC)
+#endif
#define DEADLINE_MODE_IS_ON(x) ((x)->flags & TC_ETF_DEADLINE_MODE_ON)
#define OFFLOAD_IS_ON(x) ((x)->flags & TC_ETF_OFFLOAD_ON)
#define SKIP_SOCK_CHECK_IS_SET(x) ((x)->flags & TC_ETF_SKIP_SOCK_CHECK)
@@ -128,8 +133,9 @@ static void reset_watchdog(struct Qdisc *sch)
return;
}

- next = ktime_sub_ns(skb->tstamp, q->delta);
- qdisc_watchdog_schedule_ns(&q->watchdog, ktime_to_ns(next));
+ next = ktime_sub_ns(skb->tstamp, q->delta + NET_SCH_ETF_TIMER_RANGE);
+ qdisc_watchdog_schedule_soon_ns(&q->watchdog, ktime_to_ns(next),
+ NET_SCH_ETF_TIMER_RANGE);
}

static void report_sock_error(struct sk_buff *skb, u32 err, u8 code)
--
2.20.1