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mac80211: add new minstrel_ht patches to improve probing on mt76x2

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Signed-off-by: Felix Fietkau <nbd@nbd.name>
master
Felix Fietkau 5 years ago
parent 98b654de2e
commit 9861050b85
4 changed files with 591 additions and 0 deletions
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22
package/kernel/mac80211/patches/subsys/363-mac80211-minstrel_ht-fix-per-group-max-throughput-ra.patch
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From: Felix Fietkau <nbd@nbd.name>
Date: Fri, 14 Jun 2019 21:12:04 +0200
Subject: [PATCH] mac80211: minstrel_ht: fix per-group max throughput rate
initialization
The group number needs to be multiplied by the number of rates per group
to get the full rate index
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/net/mac80211/rc80211_minstrel_ht.c
+++ b/net/mac80211/rc80211_minstrel_ht.c
@@ -576,7 +576,7 @@ minstrel_ht_update_stats(struct minstrel
/* (re)Initialize group rate indexes */
for(j = 0; j < MAX_THR_RATES; j++)
- tmp_group_tp_rate[j] = group;
+ tmp_group_tp_rate[j] = MCS_GROUP_RATES * group;
for (i = 0; i < MCS_GROUP_RATES; i++) {
if (!(mi->supported[group] & BIT(i)))

42
package/kernel/mac80211/patches/subsys/364-mac80211-minstrel_ht-reduce-unnecessary-rate-probing.patch
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From: Felix Fietkau <nbd@nbd.name>
Date: Wed, 5 Jun 2019 20:42:49 +0200
Subject: [PATCH] mac80211: minstrel_ht: reduce unnecessary rate probing
attempts
On hardware with static fallback tables (e.g. mt76x2), rate probing attempts
can be very expensive.
On such devices, avoid sampling rates slower than the per-group max throughput
rate, based on the assumption that the fallback table will take care of probing
lower rates within that group if the higher rates fail.
To make this work, this also fixes a wrong initialization in the previously
unused per-group sorted rate array.
To further reduce unnecessary probing attempts, skip duplicate attempts on
rates slower than the max throughput rate.
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/net/mac80211/rc80211_minstrel_ht.c
+++ b/net/mac80211/rc80211_minstrel_ht.c
@@ -1062,6 +1062,21 @@ minstrel_get_sample_rate(struct minstrel
minstrel_get_duration(mi->max_prob_rate) * 3 < sample_dur)
return -1;
+
+ /*
+ * For devices with no configurable multi-rate retry, skip sampling
+ * below the per-group max throughput rate, and only use one sampling
+ * attempt per rate
+ */
+ if (mp->hw->max_rates == 1 &&
+ (minstrel_get_duration(mg->max_group_tp_rate[0]) < sample_dur ||
+ mrs->attempts))
+ return -1;
+
+ /* Skip already sampled slow rates */
+ if (sample_dur >= minstrel_get_duration(tp_rate1) && mrs->attempts)
+ return -1;
+
/*
* Make sure that lower rates get sampled only occasionally,
* if the link is working perfectly.

46
package/kernel/mac80211/patches/subsys/365-mac80211-minstrel_ht-fix-default-max-throughput-rate.patch
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From: Felix Fietkau <nbd@nbd.name>
Date: Fri, 14 Jun 2019 21:14:22 +0200
Subject: [PATCH] mac80211: minstrel_ht: fix default max throughput rate
indexes
Use the first supported rate instead of 0 (which can be invalid)
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/net/mac80211/rc80211_minstrel_ht.c
+++ b/net/mac80211/rc80211_minstrel_ht.c
@@ -487,7 +487,7 @@ minstrel_ht_assign_best_tp_rates(struct
tmp_prob = mi->groups[tmp_group].rates[tmp_idx].prob_ewma;
tmp_mcs_tp = minstrel_ht_get_tp_avg(mi, tmp_group, tmp_idx, tmp_prob);
- if (tmp_cck_tp > tmp_mcs_tp) {
+ if (tmp_cck_tp_rate && tmp_cck_tp > tmp_mcs_tp) {
for(i = 0; i < MAX_THR_RATES; i++) {
minstrel_ht_sort_best_tp_rates(mi, tmp_cck_tp_rate[i],
tmp_mcs_tp_rate);
@@ -559,11 +559,19 @@ minstrel_ht_update_stats(struct minstrel
mi->sample_slow = 0;
mi->sample_count = 0;
- /* Initialize global rate indexes */
- for(j = 0; j < MAX_THR_RATES; j++){
- tmp_mcs_tp_rate[j] = 0;
- tmp_cck_tp_rate[j] = 0;
- }
+ memset(tmp_mcs_tp_rate, 0, sizeof(tmp_mcs_tp_rate));
+ memset(tmp_cck_tp_rate, 0, sizeof(tmp_cck_tp_rate));
+ if (mi->supported[MINSTREL_CCK_GROUP])
+ for (j = 0; j < ARRAY_SIZE(tmp_cck_tp_rate); j++)
+ tmp_cck_tp_rate[j] = MINSTREL_CCK_GROUP * MCS_GROUP_RATES;
+
+ if (mi->supported[MINSTREL_VHT_GROUP_0])
+ index = MINSTREL_VHT_GROUP_0 * MCS_GROUP_RATES;
+ else
+ index = MINSTREL_HT_GROUP_0 * MCS_GROUP_RATES;
+
+ for (j = 0; j < ARRAY_SIZE(tmp_mcs_tp_rate); j++)
+ tmp_mcs_tp_rate[j] = index;
/* Find best rate sets within all MCS groups*/
for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {

481
package/kernel/mac80211/patches/subsys/366-mac80211-minstrel_ht-improve-rate-probing-for-device.patch
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From: Felix Fietkau <nbd@nbd.name>
Date: Fri, 14 Jun 2019 21:15:47 +0200
Subject: [PATCH] mac80211: minstrel_ht: improve rate probing for devices
with static fallback
On some devices that only support static rate fallback tables sending rate
control probing packets can be really expensive.
Probing lower rates can already hurt throughput quite a bit. What hurts even
more is the fact that on mt76x0/mt76x2, single probing packets can only be
forced by directing packets at a different internal hardware queue, which
causes some heavy reordering and extra latency.
The reordering issue is mainly problematic while pushing lots of packets to
a particular station. If there is little activity, the overhead of probing is
neglegible.
The static fallback behavior is designed to pretty much only handle rate
control algorithms that use only a very limited set of rates on which the
algorithm switches up/down based on packet error rate.
In order to better support that kind of hardware, this patch implements a
different approach to rate probing where it switches to a slightly higher rate,
waits for tx status feedback, then updates the stats and switches back to
the new max throughput rate. This only triggers above a packet rate of 100
per stats interval (~50ms).
For that kind of probing, the code has to reduce the set of probing rates
a lot more compared to single packet probing, so it uses only one packet
per MCS group which is either slightly faster, or as close as possible to
the max throughput rate.
This allows switching between similar rates with different numbers of
streams. The algorithm assumes that the hardware will work its way lower
within an MCS group in case of retransmissions, so that lower rates don't
have to be probed by the high packets per second rate probing code.
To further reduce the search space, it also does not probe rates with lower
channel bandwidth than the max throughput rate.
At the moment, these changes will only affect mt76x0/mt76x2.
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/net/mac80211/rc80211_minstrel.h
+++ b/net/mac80211/rc80211_minstrel.h
@@ -114,6 +114,7 @@ struct minstrel_sta_info {
struct minstrel_priv {
struct ieee80211_hw *hw;
bool has_mrr;
+ u32 sample_switch;
unsigned int cw_min;
unsigned int cw_max;
unsigned int max_retry;
--- a/net/mac80211/rc80211_minstrel_ht.c
+++ b/net/mac80211/rc80211_minstrel_ht.c
@@ -21,6 +21,8 @@
#define AVG_AMPDU_SIZE 16
#define AVG_PKT_SIZE 1200
+#define SAMPLE_SWITCH_THR 100
+
/* Number of bits for an average sized packet */
#define MCS_NBITS ((AVG_PKT_SIZE * AVG_AMPDU_SIZE) << 3)
@@ -59,6 +61,7 @@
[GROUP_IDX(_streams, _sgi, _ht40)] = { \
.streams = _streams, \
.shift = _s, \
+ .bw = _ht40, \
.flags = \
IEEE80211_TX_RC_MCS | \
(_sgi ? IEEE80211_TX_RC_SHORT_GI : 0) | \
@@ -95,6 +98,7 @@
[VHT_GROUP_IDX(_streams, _sgi, _bw)] = { \
.streams = _streams, \
.shift = _s, \
+ .bw = _bw, \
.flags = \
IEEE80211_TX_RC_VHT_MCS | \
(_sgi ? IEEE80211_TX_RC_SHORT_GI : 0) | \
@@ -527,6 +531,133 @@ minstrel_ht_prob_rate_reduce_streams(str
}
}
+static inline int
+minstrel_get_duration(int index)
+{
+ const struct mcs_group *group = &minstrel_mcs_groups[index / MCS_GROUP_RATES];
+ unsigned int duration = group->duration[index % MCS_GROUP_RATES];
+ return duration << group->shift;
+}
+
+static bool
+minstrel_ht_probe_group(struct minstrel_ht_sta *mi, const struct mcs_group *tp_group,
+ int tp_idx, const struct mcs_group *group)
+{
+ if (group->bw < tp_group->bw)
+ return false;
+
+ if (group->streams == tp_group->streams)
+ return true;
+
+ if (tp_idx < 4 && group->streams == tp_group->streams - 1)
+ return true;
+
+ return group->streams == tp_group->streams + 1;
+}
+
+static void
+minstrel_ht_find_probe_rates(struct minstrel_ht_sta *mi, u16 *rates, int *n_rates,
+ bool faster_rate)
+{
+ const struct mcs_group *group, *tp_group;
+ int i, g, max_dur;
+ int tp_idx;
+
+ tp_group = &minstrel_mcs_groups[mi->max_tp_rate[0] / MCS_GROUP_RATES];
+ tp_idx = mi->max_tp_rate[0] % MCS_GROUP_RATES;
+
+ max_dur = minstrel_get_duration(mi->max_tp_rate[0]);
+ if (faster_rate)
+ max_dur -= max_dur / 16;
+
+ for (g = 0; g < MINSTREL_GROUPS_NB; g++) {
+ u16 supported = mi->supported[g];
+
+ if (!supported)
+ continue;
+
+ group = &minstrel_mcs_groups[g];
+ if (!minstrel_ht_probe_group(mi, tp_group, tp_idx, group))
+ continue;
+
+ for (i = 0; supported; supported >>= 1, i++) {
+ int idx;
+
+ if (!(supported & 1))
+ continue;
+
+ if ((group->duration[i] << group->shift) > max_dur)
+ continue;
+
+ idx = g * MCS_GROUP_RATES + i;
+ if (idx == mi->max_tp_rate[0])
+ continue;
+
+ rates[(*n_rates)++] = idx;
+ break;
+ }
+ }
+}
+
+static void
+minstrel_ht_rate_sample_switch(struct minstrel_priv *mp,
+ struct minstrel_ht_sta *mi)
+{
+ struct minstrel_rate_stats *mrs;
+ u16 rates[MINSTREL_GROUPS_NB];
+ int n_rates = 0;
+ int probe_rate = 0;
+ bool faster_rate;
+ int i;
+ u8 random;
+
+ /*
+ * Use rate switching instead of probing packets for devices with
+ * little control over retry fallback behavior
+ */
+ if (mp->hw->max_rates > 1)
+ return;
+
+ /*
+ * If the current EWMA prob is >75%, look for a rate that's 6.25%
+ * faster than the max tp rate.
+ * If that fails, look again for a rate that is at least as fast
+ */
+ mrs = minstrel_get_ratestats(mi, mi->max_tp_rate[0]);
+ faster_rate = mrs->prob_ewma > MINSTREL_FRAC(75, 100);
+ minstrel_ht_find_probe_rates(mi, rates, &n_rates, faster_rate);
+ if (!n_rates && faster_rate)
+ minstrel_ht_find_probe_rates(mi, rates, &n_rates, false);
+
+ /* If no suitable rate was found, try to pick the next one in the group */
+ if (!n_rates) {
+ int g_idx = mi->max_tp_rate[0] / MCS_GROUP_RATES;
+ u16 supported = mi->supported[g_idx];
+
+ supported >>= mi->max_tp_rate[0] % MCS_GROUP_RATES;
+ for (i = 0; supported; i++) {
+ if (!(supported & 1))
+ continue;
+
+ probe_rate = mi->max_tp_rate[0] + i;
+ goto out;
+ }
+
+ return;
+ }
+
+ i = 0;
+ if (n_rates > 1) {
+ random = prandom_u32();
+ i = random % n_rates;
+ }
+ probe_rate = rates[i];
+
+out:
+ mi->sample_rate = probe_rate;
+ mi->sample_mode = MINSTREL_SAMPLE_ACTIVE;
+}
+
/*
* Update rate statistics and select new primary rates
*
@@ -537,7 +668,8 @@ minstrel_ht_prob_rate_reduce_streams(str
* higher throughput rates, even if the probablity is a bit lower
*/
static void
-minstrel_ht_update_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
+minstrel_ht_update_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
+ bool sample)
{
struct minstrel_mcs_group_data *mg;
struct minstrel_rate_stats *mrs;
@@ -545,6 +677,18 @@ minstrel_ht_update_stats(struct minstrel
u16 tmp_mcs_tp_rate[MAX_THR_RATES], tmp_group_tp_rate[MAX_THR_RATES];
u16 tmp_cck_tp_rate[MAX_THR_RATES], index;
+ mi->sample_mode = MINSTREL_SAMPLE_IDLE;
+
+ if (sample) {
+ mi->total_packets_cur = mi->total_packets -
+ mi->total_packets_last;
+ mi->total_packets_last = mi->total_packets;
+ }
+ if (!mp->sample_switch)
+ sample = false;
+ if (mi->total_packets_cur < SAMPLE_SWITCH_THR && mp->sample_switch != 1)
+ sample = false;
+
if (mi->ampdu_packets > 0) {
if (!ieee80211_hw_check(mp->hw, TX_STATUS_NO_AMPDU_LEN))
mi->avg_ampdu_len = minstrel_ewma(mi->avg_ampdu_len,
@@ -631,12 +775,16 @@ minstrel_ht_update_stats(struct minstrel
/* try to sample all available rates during each interval */
mi->sample_count *= 8;
+ if (sample)
+ minstrel_ht_rate_sample_switch(mp, mi);
+
#ifdef CPTCFG_MAC80211_DEBUGFS
/* use fixed index if set */
if (mp->fixed_rate_idx != -1) {
for (i = 0; i < 4; i++)
mi->max_tp_rate[i] = mp->fixed_rate_idx;
mi->max_prob_rate = mp->fixed_rate_idx;
+ mi->sample_mode = MINSTREL_SAMPLE_IDLE;
}
#endif
@@ -740,15 +888,17 @@ minstrel_ht_tx_status(void *priv, struct
struct minstrel_ht_sta_priv *msp = priv_sta;
struct minstrel_ht_sta *mi = &msp->ht;
struct ieee80211_tx_rate *ar = info->status.rates;
- struct minstrel_rate_stats *rate, *rate2;
+ struct minstrel_rate_stats *rate, *rate2, *rate_sample = NULL;
struct minstrel_priv *mp = priv;
bool last, update = false;
+ bool sample_status = false;
int i;
if (!msp->is_ht)
return mac80211_minstrel.tx_status_ext(priv, sband,
&msp->legacy, st);
+
/* This packet was aggregated but doesn't carry status info */
if ((info->flags & IEEE80211_TX_CTL_AMPDU) &&
!(info->flags & IEEE80211_TX_STAT_AMPDU))
@@ -774,12 +924,17 @@ minstrel_ht_tx_status(void *priv, struct
if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
mi->sample_packets += info->status.ampdu_len;
+ if (mi->sample_mode != MINSTREL_SAMPLE_IDLE)
+ rate_sample = minstrel_get_ratestats(mi, mi->sample_rate);
+
last = !minstrel_ht_txstat_valid(mp, &ar[0]);
for (i = 0; !last; i++) {
last = (i == IEEE80211_TX_MAX_RATES - 1) ||
!minstrel_ht_txstat_valid(mp, &ar[i + 1]);
rate = minstrel_ht_get_stats(mp, mi, &ar[i]);
+ if (rate == rate_sample)
+ sample_status = true;
if (last)
rate->success += info->status.ampdu_ack_len;
@@ -787,44 +942,60 @@ minstrel_ht_tx_status(void *priv, struct
rate->attempts += ar[i].count * info->status.ampdu_len;
}
- /*
- * check for sudden death of spatial multiplexing,
- * downgrade to a lower number of streams if necessary.
- */
- rate = minstrel_get_ratestats(mi, mi->max_tp_rate[0]);
- if (rate->attempts > 30 &&
- MINSTREL_FRAC(rate->success, rate->attempts) <
- MINSTREL_FRAC(20, 100)) {
- minstrel_downgrade_rate(mi, &mi->max_tp_rate[0], true);
+ switch (mi->sample_mode) {
+ case MINSTREL_SAMPLE_IDLE:
+ break;
+
+ case MINSTREL_SAMPLE_ACTIVE:
+ if (!sample_status)
+ break;
+
+ mi->sample_mode = MINSTREL_SAMPLE_PENDING;
update = true;
- }
+ break;
+
+ case MINSTREL_SAMPLE_PENDING:
+ if (sample_status)
+ break;
- rate2 = minstrel_get_ratestats(mi, mi->max_tp_rate[1]);
- if (rate2->attempts > 30 &&
- MINSTREL_FRAC(rate2->success, rate2->attempts) <
- MINSTREL_FRAC(20, 100)) {
- minstrel_downgrade_rate(mi, &mi->max_tp_rate[1], false);
update = true;
+ minstrel_ht_update_stats(mp, mi, false);
+ break;
+ }
+
+
+ if (mp->hw->max_rates > 1) {
+ /*
+ * check for sudden death of spatial multiplexing,
+ * downgrade to a lower number of streams if necessary.
+ */
+ rate = minstrel_get_ratestats(mi, mi->max_tp_rate[0]);
+ if (rate->attempts > 30 &&
+ MINSTREL_FRAC(rate->success, rate->attempts) <
+ MINSTREL_FRAC(20, 100)) {
+ minstrel_downgrade_rate(mi, &mi->max_tp_rate[0], true);
+ update = true;
+ }
+
+ rate2 = minstrel_get_ratestats(mi, mi->max_tp_rate[1]);
+ if (rate2->attempts > 30 &&
+ MINSTREL_FRAC(rate2->success, rate2->attempts) <
+ MINSTREL_FRAC(20, 100)) {
+ minstrel_downgrade_rate(mi, &mi->max_tp_rate[1], false);
+ update = true;
+ }
}
if (time_after(jiffies, mi->last_stats_update +
(mp->update_interval / 2 * HZ) / 1000)) {
update = true;
- minstrel_ht_update_stats(mp, mi);
+ minstrel_ht_update_stats(mp, mi, true);
}
if (update)
minstrel_ht_update_rates(mp, mi);
}
-static inline int
-minstrel_get_duration(int index)
-{
- const struct mcs_group *group = &minstrel_mcs_groups[index / MCS_GROUP_RATES];
- unsigned int duration = group->duration[index % MCS_GROUP_RATES];
- return duration << group->shift;
-}
-
static void
minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
int index)
@@ -989,14 +1160,18 @@ static void
minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
{
struct ieee80211_sta_rates *rates;
+ u16 first_rate = mi->max_tp_rate[0];
int i = 0;
+ if (mi->sample_mode == MINSTREL_SAMPLE_ACTIVE)
+ first_rate = mi->sample_rate;
+
rates = kzalloc(sizeof(*rates), GFP_ATOMIC);
if (!rates)
return;
/* Start with max_tp_rate[0] */
- minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_tp_rate[0]);
+ minstrel_ht_set_rate(mp, mi, rates, i++, first_rate);
if (mp->hw->max_rates >= 3) {
/* At least 3 tx rates supported, use max_tp_rate[1] next */
@@ -1023,6 +1198,11 @@ minstrel_get_sample_rate(struct minstrel
int tp_rate1, tp_rate2;
int sample_idx = 0;
+ if (mp->hw->max_rates == 1 && mp->sample_switch &&
+ (mi->total_packets_cur >= SAMPLE_SWITCH_THR ||
+ mp->sample_switch == 1))
+ return -1;
+
if (mi->sample_wait > 0) {
mi->sample_wait--;
return -1;
@@ -1349,7 +1529,7 @@ minstrel_ht_update_caps(void *priv, stru
mi->supported[MINSTREL_CCK_GROUP] |= mi->cck_supported_short << 4;
/* create an initial rate table with the lowest supported rates */
- minstrel_ht_update_stats(mp, mi);
+ minstrel_ht_update_stats(mp, mi, true);
minstrel_ht_update_rates(mp, mi);
return;
@@ -1467,6 +1647,8 @@ minstrel_ht_alloc(struct ieee80211_hw *h
if (!mp)
return NULL;
+ mp->sample_switch = -1;
+
/* contention window settings
* Just an approximation. Using the per-queue values would complicate
* the calculations and is probably unnecessary */
@@ -1498,6 +1680,8 @@ minstrel_ht_alloc(struct ieee80211_hw *h
mp->fixed_rate_idx = (u32) -1;
debugfs_create_u32("fixed_rate_idx", S_IRUGO | S_IWUGO, debugfsdir,
&mp->fixed_rate_idx);
+ debugfs_create_u32("sample_switch", S_IRUGO | S_IWUSR, debugfsdir,
+ &mp->sample_switch);
#endif
minstrel_ht_init_cck_rates(mp);
--- a/net/mac80211/rc80211_minstrel_ht.h
+++ b/net/mac80211/rc80211_minstrel_ht.h
@@ -36,6 +36,7 @@ struct mcs_group {
u16 flags;
u8 streams;
u8 shift;
+ u8 bw;
u16 duration[MCS_GROUP_RATES];
};
@@ -53,6 +54,12 @@ struct minstrel_mcs_group_data {
struct minstrel_rate_stats rates[MCS_GROUP_RATES];
};
+enum minstrel_sample_mode {
+ MINSTREL_SAMPLE_IDLE,
+ MINSTREL_SAMPLE_ACTIVE,
+ MINSTREL_SAMPLE_PENDING,
+};
+
struct minstrel_ht_sta {
struct ieee80211_sta *sta;
@@ -74,6 +81,8 @@ struct minstrel_ht_sta {
unsigned int overhead;
unsigned int overhead_rtscts;
+ unsigned int total_packets_last;
+ unsigned int total_packets_cur;
unsigned int total_packets;
unsigned int sample_packets;
@@ -85,6 +94,9 @@ struct minstrel_ht_sta {
u8 sample_count;
u8 sample_slow;
+ enum minstrel_sample_mode sample_mode;
+ u16 sample_rate;
+
/* current MCS group to be sampled */
u8 sample_group;
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