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Commit 06171e9c authored by Felix Fietkau's avatar Felix Fietkau Committed by Johannes Berg
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mac80211: minstrel_ht: improve sample rate skip logic 



There were a few issues that were slowing down the process of finding
the optimal rate, especially on devices with multi-rate retry
limitations:

When max_tp_rate[0] was slower than max_tp_rate[1], the code did not
sample max_tp_rate[1], which would often allow it to switch places with
max_tp_rate[0] (e.g. if only the first sampling attempts were bad, but the
rate is otherwise good).

Also, sample attempts of rates between max_tp_rate[0] and [1] were being
ignored in this case, because the code only checked if the rate was
slower than [1].

Fix this by checking against the fastest / second fastest max_tp_rate
instead of assuming a specific order between the two.

In my tests this patch significantly reduces the time until minstrel_ht
finds the optimal rate right after assoc

Signed-off-by: default avatarFelix Fietkau <nbd@openwrt.org>
Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 07310a63

net/mac80211/rc80211_minstrel_ht.c

+16 −7
Original line number Diff line number Diff line
@@ -924,6 +924,7 @@ minstrel_get_sample_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi) 
	struct minstrel_rate_stats *mrs;

	struct minstrel_mcs_group_data *mg;

	unsigned int sample_dur, sample_group, cur_max_tp_streams;

	int tp_rate1, tp_rate2;

	int sample_idx = 0;



	if (mi->sample_wait > 0) {
@@ -945,14 +946,22 @@ minstrel_get_sample_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi) 
	mrs = &mg->rates[sample_idx];

	sample_idx += sample_group * MCS_GROUP_RATES;



	/* Set tp_rate1, tp_rate2 to the highest / second highest max_tp_rate */

	if (minstrel_get_duration(mi->max_tp_rate[0]) >

	    minstrel_get_duration(mi->max_tp_rate[1])) {

		tp_rate1 = mi->max_tp_rate[1];

		tp_rate2 = mi->max_tp_rate[0];

	} else {

		tp_rate1 = mi->max_tp_rate[0];

		tp_rate2 = mi->max_tp_rate[1];

	}



	/*

	 * Sampling might add some overhead (RTS, no aggregation)

	 * to the frame. Hence, don't use sampling for the currently

	 * used rates.

	 * to the frame. Hence, don't use sampling for the highest currently

	 * used highest throughput or probability rate.

	 */

	if (sample_idx == mi->max_tp_rate[0] ||

	    sample_idx == mi->max_tp_rate[1] ||

	    sample_idx == mi->max_prob_rate)

	if (sample_idx == mi->max_tp_rate[0] || sample_idx == mi->max_prob_rate)

		return -1;



	/*
@@ -967,10 +976,10 @@ minstrel_get_sample_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi) 
	 * if the link is working perfectly.

	 */



	cur_max_tp_streams = minstrel_mcs_groups[mi->max_tp_rate[0] /

	cur_max_tp_streams = minstrel_mcs_groups[tp_rate1 /

		MCS_GROUP_RATES].streams;

	sample_dur = minstrel_get_duration(sample_idx);

	if (sample_dur >= minstrel_get_duration(mi->max_tp_rate[1]) &&

	if (sample_dur >= minstrel_get_duration(tp_rate2) &&

	    (cur_max_tp_streams - 1 <

	     minstrel_mcs_groups[sample_group].streams ||

	     sample_dur >= minstrel_get_duration(mi->max_prob_rate))) {