2021-12-17 11:43:10

by Felix Fietkau

Subject: [PATCH] mac80211: use coarse boottime for airtime fairness code

The time values used by the airtime fairness code only need to be accurate
enough to cover station activity detection.
Using ktime_get_coarse_boottime_ns instead of ktime_get_boottime_ns will
drop the accuracy down to jiffies intervals, but at the same time saves
a lot of CPU cycles in a hot path

Signed-off-by: Felix Fietkau <[email protected]>
---
net/mac80211/tx.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 278945e3e08a..cbe7d1d00a50 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3821,7 +3821,7 @@ struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
{
struct ieee80211_local *local = hw_to_local(hw);
struct airtime_sched_info *air_sched;
- u64 now = ktime_get_boottime_ns();
+ u64 now = ktime_get_coarse_boottime_ns();
struct ieee80211_txq *ret = NULL;
struct airtime_info *air_info;
struct txq_info *txqi = NULL;
@@ -3948,7 +3948,7 @@ void ieee80211_update_airtime_weight(struct ieee80211_local *local,
u64 weight_sum = 0;

if (unlikely(!now))
- now = ktime_get_boottime_ns();
+ now = ktime_get_coarse_boottime_ns();

lockdep_assert_held(&air_sched->lock);

@@ -3974,7 +3974,7 @@ void ieee80211_schedule_txq(struct ieee80211_hw *hw,
struct ieee80211_local *local = hw_to_local(hw);
struct txq_info *txqi = to_txq_info(txq);
struct airtime_sched_info *air_sched;
- u64 now = ktime_get_boottime_ns();
+ u64 now = ktime_get_coarse_boottime_ns();
struct airtime_info *air_info;
u8 ac = txq->ac;
bool was_active;
@@ -4032,7 +4032,7 @@ static void __ieee80211_unschedule_txq(struct ieee80211_hw *hw,

if (!purge)
airtime_set_active(air_sched, air_info,
- ktime_get_boottime_ns());
+ ktime_get_coarse_boottime_ns());

rb_erase_cached(&txqi->schedule_order,
&air_sched->active_txqs);
@@ -4120,7 +4120,7 @@ bool ieee80211_txq_may_transmit(struct ieee80211_hw *hw,
if (RB_EMPTY_NODE(&txqi->schedule_order))
goto out;

- now = ktime_get_boottime_ns();
+ now = ktime_get_coarse_boottime_ns();

/* Like in ieee80211_next_txq(), make sure the first station in the
* scheduling order is eligible for transmission to avoid starvation.
--
2.34.1

2021-12-17 12:22:58

by Toke Høiland-Jørgensen

Subject: Re: [PATCH] mac80211: use coarse boottime for airtime fairness code

Felix Fietkau <[email protected]> writes:

> The time values used by the airtime fairness code only need to be accurate
> enough to cover station activity detection.
> Using ktime_get_coarse_boottime_ns instead of ktime_get_boottime_ns will
> drop the accuracy down to jiffies intervals, but at the same time saves
> a lot of CPU cycles in a hot path
>
> Signed-off-by: Felix Fietkau <[email protected]>

Makes sense for the activity detection stuff!

Acked-by: Toke Høiland-Jørgensen <[email protected]>