In order for the Fq_CoDel algorithm integrated in mac80211 layer to operate
effectively to control excessive queueing latency, the CoDel algorithm
requires an accurate measure of how long packets stays in the queue, AKA
sojourn time. The sojourn time measured at the mac80211 layer doesn't
include queueing latency in the lower layer (firmware/hardware) and CoDel
expects lower layer to have a short queue. However, most 802.11ac chipsets
offload tasks such TX aggregation to firmware or hardware, thus have a deep
lower layer queue.
Without a mechanism to control the lower layer queue size, packets only
stay in mac80211 layer transiently before being sent to firmware queue.
As a result, the sojourn time measured by CoDel in the mac80211 layer is
almost always lower than the CoDel latency target, hence CoDel does little
to control the latency, even when the lower layer queue causes excessive
latency.
The Byte Queue Limits (BQL) mechanism is commonly used to address the
similar issue with wired network interface. However, this method cannot be
applied directly to the wireless network interface. "Bytes" is not a
suitable measure of queue depth in the wireless network, as the data rate
can vary dramatically from station to station in the same network, from a
few Mbps to over Gbps.
This patch implements an Airtime-based Queue Limit (AQL) to make CoDel work
effectively with wireless drivers that utilized firmware/hardware
offloading. AQL allows each txq to release just enough packets to the lower
layer to form 1-2 large aggregations to keep hardware fully utilized and
retains the rest of the frames in mac80211 layer to be controlled by the
CoDel algorithm.
Signed-off-by: Kan Yan <[email protected]>
[ Toke: Keep API to set pending airtime internal, fix nits in commit msg ]
Signed-off-by: Toke Høiland-Jørgensen <[email protected]>
---
include/net/cfg80211.h | 7 ++++
include/net/mac80211.h | 12 ++++++
net/mac80211/debugfs.c | 78 ++++++++++++++++++++++++++++++++++++++
net/mac80211/debugfs_sta.c | 43 ++++++++++++++++-----
net/mac80211/ieee80211_i.h | 4 ++
net/mac80211/main.c | 10 ++++-
net/mac80211/sta_info.c | 40 +++++++++++++++++++
net/mac80211/sta_info.h | 8 ++++
net/mac80211/tx.c | 47 +++++++++++++++++++++--
9 files changed, 235 insertions(+), 14 deletions(-)
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 4ab2c49423dc..15f9f04de149 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -2602,6 +2602,13 @@ enum wiphy_params_flags {
#define IEEE80211_DEFAULT_AIRTIME_WEIGHT 256
+/* The per TXQ device queue limit in airtime */
+#define IEEE80211_DEFAULT_AQL_TXQ_LIMIT_L 4000
+#define IEEE80211_DEFAULT_AQL_TXQ_LIMIT_H 8000
+
+/* The per interface airtime threshold to switch to lower queue limit */
+#define IEEE80211_AQL_THRESHOLD 24000
+
/**
* struct cfg80211_pmksa - PMK Security Association
*
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 4319596ef472..269be699e89c 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -5558,6 +5558,18 @@ void ieee80211_send_eosp_nullfunc(struct ieee80211_sta *pubsta, int tid);
void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
u32 tx_airtime, u32 rx_airtime);
+/**
+ * ieee80211_txq_airtime_check - check if a txq can send frame to device
+ *
+ * @hw: pointer obtained from ieee80211_alloc_hw()
+ * @txq: pointer obtained from station or virtual interface
+ *
+ * Return true if the AQL's airtime limit has not been reached and the txq can
+ * continue to send more packets to the device. Otherwise return false.
+ */
+bool
+ieee80211_txq_airtime_check(struct ieee80211_hw *hw, struct ieee80211_txq *txq);
+
/**
* ieee80211_iter_keys - iterate keys programmed into the device
* @hw: pointer obtained from ieee80211_alloc_hw()
diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index 568b3b276931..d77ea0e51c1d 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -148,6 +148,80 @@ static const struct file_operations aqm_ops = {
.llseek = default_llseek,
};
+static ssize_t aql_txq_limit_read(struct file *file,
+ char __user *user_buf,
+ size_t count,
+ loff_t *ppos)
+{
+ struct ieee80211_local *local = file->private_data;
+ char buf[400];
+ int len = 0;
+
+ len = scnprintf(buf, sizeof(buf),
+ "AC AQL limit low AQL limit high\n"
+ "VO %u %u\n"
+ "VI %u %u\n"
+ "BE %u %u\n"
+ "BK %u %u\n",
+ local->aql_txq_limit_low[IEEE80211_AC_VO],
+ local->aql_txq_limit_high[IEEE80211_AC_VO],
+ local->aql_txq_limit_low[IEEE80211_AC_VI],
+ local->aql_txq_limit_high[IEEE80211_AC_VI],
+ local->aql_txq_limit_low[IEEE80211_AC_BE],
+ local->aql_txq_limit_high[IEEE80211_AC_BE],
+ local->aql_txq_limit_low[IEEE80211_AC_BK],
+ local->aql_txq_limit_high[IEEE80211_AC_BK]);
+ return simple_read_from_buffer(user_buf, count, ppos,
+ buf, len);
+}
+
+static ssize_t aql_txq_limit_write(struct file *file,
+ const char __user *user_buf,
+ size_t count,
+ loff_t *ppos)
+{
+ struct ieee80211_local *local = file->private_data;
+ char buf[100];
+ size_t len;
+ u32 ac, q_limit_low, q_limit_high;
+ struct sta_info *sta;
+
+ if (count > sizeof(buf))
+ return -EINVAL;
+
+ if (copy_from_user(buf, user_buf, count))
+ return -EFAULT;
+
+ buf[sizeof(buf) - 1] = 0;
+ len = strlen(buf);
+ if (len > 0 && buf[len - 1] == '\n')
+ buf[len - 1] = 0;
+
+ if (sscanf(buf, "%u %u %u", &ac, &q_limit_low, &q_limit_high) != 3)
+ return -EINVAL;
+
+ if (ac >= IEEE80211_NUM_ACS)
+ return -EINVAL;
+
+ local->aql_txq_limit_low[ac] = q_limit_low;
+ local->aql_txq_limit_high[ac] = q_limit_high;
+
+ mutex_lock(&local->sta_mtx);
+ list_for_each_entry(sta, &local->sta_list, list) {
+ sta->airtime[ac].aql_limit_low = q_limit_low;
+ sta->airtime[ac].aql_limit_high = q_limit_high;
+ }
+ mutex_unlock(&local->sta_mtx);
+ return count;
+}
+
+static const struct file_operations aql_txq_limit_ops = {
+ .write = aql_txq_limit_write,
+ .read = aql_txq_limit_read,
+ .open = simple_open,
+ .llseek = default_llseek,
+};
+
static ssize_t force_tx_status_read(struct file *file,
char __user *user_buf,
size_t count,
@@ -441,6 +515,10 @@ void debugfs_hw_add(struct ieee80211_local *local)
debugfs_create_u16("airtime_flags", 0600,
phyd, &local->airtime_flags);
+ DEBUGFS_ADD(aql_txq_limit);
+ debugfs_create_u32("aql_threshold", 0600,
+ phyd, &local->aql_threshold);
+
statsd = debugfs_create_dir("statistics", phyd);
/* if the dir failed, don't put all the other things into the root! */
diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
index c8ad20c28c43..0185e6e5e5d1 100644
--- a/net/mac80211/debugfs_sta.c
+++ b/net/mac80211/debugfs_sta.c
@@ -197,10 +197,12 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
{
struct sta_info *sta = file->private_data;
struct ieee80211_local *local = sta->sdata->local;
- size_t bufsz = 200;
+ size_t bufsz = 400;
char *buf = kzalloc(bufsz, GFP_KERNEL), *p = buf;
u64 rx_airtime = 0, tx_airtime = 0;
s64 deficit[IEEE80211_NUM_ACS];
+ u32 q_depth[IEEE80211_NUM_ACS];
+ u32 q_limit_l[IEEE80211_NUM_ACS], q_limit_h[IEEE80211_NUM_ACS];
ssize_t rv;
int ac;
@@ -212,19 +214,22 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
rx_airtime += sta->airtime[ac].rx_airtime;
tx_airtime += sta->airtime[ac].tx_airtime;
deficit[ac] = sta->airtime[ac].deficit;
+ q_limit_l[ac] = sta->airtime[ac].aql_limit_low;
+ q_limit_h[ac] = sta->airtime[ac].aql_limit_high;
spin_unlock_bh(&local->active_txq_lock[ac]);
+ q_depth[ac] = atomic_read(&sta->airtime[ac].aql_tx_pending);
}
p += scnprintf(p, bufsz + buf - p,
"RX: %llu us\nTX: %llu us\nWeight: %u\n"
- "Deficit: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n",
- rx_airtime,
- tx_airtime,
- sta->airtime_weight,
- deficit[0],
- deficit[1],
- deficit[2],
- deficit[3]);
+ "Deficit: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n"
+ "Q depth: VO: %u us VI: %u us BE: %u us BK: %u us\n"
+ "Q limit[low/high]: VO: %u/%u VI: %u/%u BE: %u/%u BK: %u/%u\n",
+ rx_airtime, tx_airtime, sta->airtime_weight,
+ deficit[0], deficit[1], deficit[2], deficit[3],
+ q_depth[0], q_depth[1], q_depth[2], q_depth[3],
+ q_limit_l[0], q_limit_h[0], q_limit_l[1], q_limit_h[1],
+ q_limit_l[2], q_limit_h[2], q_limit_l[3], q_limit_h[3]),
rv = simple_read_from_buffer(userbuf, count, ppos, buf, p - buf);
kfree(buf);
@@ -236,7 +241,25 @@ static ssize_t sta_airtime_write(struct file *file, const char __user *userbuf,
{
struct sta_info *sta = file->private_data;
struct ieee80211_local *local = sta->sdata->local;
- int ac;
+ u32 ac, q_limit_l, q_limit_h;
+ char _buf[100] = {}, *buf = _buf;
+
+ if (count > sizeof(_buf))
+ return -EINVAL;
+
+ if (copy_from_user(buf, userbuf, count))
+ return -EFAULT;
+
+ buf[sizeof(_buf) - 1] = '\0';
+ if (sscanf(buf, "queue limit %u %u %u", &ac, &q_limit_l, &q_limit_h)
+ != 3)
+ return -EINVAL;
+
+ if (ac >= IEEE80211_NUM_ACS)
+ return -EINVAL;
+
+ sta->airtime[ac].aql_limit_low = q_limit_l;
+ sta->airtime[ac].aql_limit_high = q_limit_h;
for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
spin_lock_bh(&local->active_txq_lock[ac]);
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 225ea4e3cd76..ad15b3be8bb3 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1142,6 +1142,10 @@ struct ieee80211_local {
u16 schedule_round[IEEE80211_NUM_ACS];
u16 airtime_flags;
+ u32 aql_txq_limit_low[IEEE80211_NUM_ACS];
+ u32 aql_txq_limit_high[IEEE80211_NUM_ACS];
+ u32 aql_threshold;
+ atomic_t aql_total_pending_airtime;
const struct ieee80211_ops *ops;
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index aba094b4ccfc..071ea92a3748 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -667,8 +667,16 @@ struct ieee80211_hw *ieee80211_alloc_hw_nm(size_t priv_data_len,
for (i = 0; i < IEEE80211_NUM_ACS; i++) {
INIT_LIST_HEAD(&local->active_txqs[i]);
spin_lock_init(&local->active_txq_lock[i]);
+ local->aql_txq_limit_low[i] = IEEE80211_DEFAULT_AQL_TXQ_LIMIT_L;
+ local->aql_txq_limit_high[i] =
+ IEEE80211_DEFAULT_AQL_TXQ_LIMIT_H;
}
- local->airtime_flags = AIRTIME_USE_TX | AIRTIME_USE_RX;
+
+ local->airtime_flags = AIRTIME_USE_TX |
+ AIRTIME_USE_RX |
+ AIRTIME_USE_AQL;
+ local->aql_threshold = IEEE80211_AQL_THRESHOLD;
+ atomic_set(&local->aql_total_pending_airtime, 0);
INIT_LIST_HEAD(&local->chanctx_list);
mutex_init(&local->chanctx_mtx);
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index bd11fef2139f..a76e935a543a 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -396,6 +396,9 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
skb_queue_head_init(&sta->ps_tx_buf[i]);
skb_queue_head_init(&sta->tx_filtered[i]);
sta->airtime[i].deficit = sta->airtime_weight;
+ atomic_set(&sta->airtime[i].aql_tx_pending, 0);
+ sta->airtime[i].aql_limit_low = local->aql_txq_limit_low[i];
+ sta->airtime[i].aql_limit_high = local->aql_txq_limit_high[i];
}
for (i = 0; i < IEEE80211_NUM_TIDS; i++)
@@ -1893,6 +1896,43 @@ void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
}
EXPORT_SYMBOL(ieee80211_sta_register_airtime);
+void ieee80211_sta_update_pending_airtime(struct ieee80211_local *local,
+ struct sta_info *sta, u8 ac,
+ u16 tx_airtime, bool tx_completed)
+{
+ if (!tx_completed) {
+ if (sta)
+ atomic_add(tx_airtime,
+ &sta->airtime[ac].aql_tx_pending);
+
+ atomic_add(tx_airtime, &local->aql_total_pending_airtime);
+ return;
+ }
+
+ if (sta) {
+ if (WARN_ONCE(atomic_read(&sta->airtime[ac].aql_tx_pending) <
+ tx_airtime,
+ "STA %pM AC %d txq pending airtime underflow: %u, %u",
+ sta->addr, ac,
+ atomic_read(&sta->airtime[ac].aql_tx_pending),
+ tx_airtime))
+ atomic_set(&sta->airtime[ac].aql_tx_pending, 0);
+ else
+ atomic_sub(tx_airtime,
+ &sta->airtime[ac].aql_tx_pending);
+ }
+
+ if (WARN_ONCE(atomic_read(&local->aql_total_pending_airtime) <
+ tx_airtime,
+ "Device %s AC %d pending airtime underflow: %u, %u",
+ wiphy_name(local->hw.wiphy), ac,
+ atomic_read(&local->aql_total_pending_airtime),
+ tx_airtime))
+ atomic_set(&local->aql_total_pending_airtime, 0);
+ else
+ atomic_sub(tx_airtime, &local->aql_total_pending_airtime);
+}
+
int sta_info_move_state(struct sta_info *sta,
enum ieee80211_sta_state new_state)
{
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 369c2dddce52..c8823bd0e55f 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -127,13 +127,21 @@ enum ieee80211_agg_stop_reason {
/* Debugfs flags to enable/disable use of RX/TX airtime in scheduler */
#define AIRTIME_USE_TX BIT(0)
#define AIRTIME_USE_RX BIT(1)
+#define AIRTIME_USE_AQL BIT(2)
struct airtime_info {
u64 rx_airtime;
u64 tx_airtime;
s64 deficit;
+ atomic_t aql_tx_pending; /* Estimated airtime for frames pending */
+ u32 aql_limit_low;
+ u32 aql_limit_high;
};
+void ieee80211_sta_update_pending_airtime(struct ieee80211_local *local,
+ struct sta_info *sta, u8 ac,
+ u16 tx_airtime, bool tx_completed);
+
struct sta_info;
/**
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 238c47be5fe4..f53d56ef535a 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3672,7 +3672,8 @@ struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
{
struct ieee80211_local *local = hw_to_local(hw);
struct ieee80211_txq *ret = NULL;
- struct txq_info *txqi = NULL;
+ struct txq_info *txqi = NULL, *head = NULL;
+ bool found_eligible_txq = false;
spin_lock_bh(&local->active_txq_lock[ac]);
@@ -3683,13 +3684,26 @@ struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
if (!txqi)
goto out;
+ if (txqi == head && !found_eligible_txq)
+ goto out;
+
+ if (!head)
+ head = txqi;
+
if (txqi->txq.sta) {
struct sta_info *sta = container_of(txqi->txq.sta,
- struct sta_info, sta);
+ struct sta_info, sta);
+ bool aql_check = ieee80211_txq_airtime_check(hw, &txqi->txq);
+ s64 deficit = sta->airtime[txqi->txq.ac].deficit;
+
+ if (aql_check)
+ found_eligible_txq = true;
- if (sta->airtime[txqi->txq.ac].deficit < 0) {
+ if (deficit < 0)
sta->airtime[txqi->txq.ac].deficit +=
sta->airtime_weight;
+
+ if (deficit < 0 || !aql_check) {
list_move_tail(&txqi->schedule_order,
&local->active_txqs[txqi->txq.ac]);
goto begin;
@@ -3743,6 +3757,33 @@ void __ieee80211_schedule_txq(struct ieee80211_hw *hw,
}
EXPORT_SYMBOL(__ieee80211_schedule_txq);
+bool ieee80211_txq_airtime_check(struct ieee80211_hw *hw,
+ struct ieee80211_txq *txq)
+{
+ struct sta_info *sta;
+ struct ieee80211_local *local = hw_to_local(hw);
+
+ if (!(local->airtime_flags & AIRTIME_USE_AQL))
+ return true;
+
+ if (!txq->sta)
+ return true;
+
+ sta = container_of(txq->sta, struct sta_info, sta);
+ if (atomic_read(&sta->airtime[txq->ac].aql_tx_pending) <
+ sta->airtime[txq->ac].aql_limit_low)
+ return true;
+
+ if (atomic_read(&local->aql_total_pending_airtime) <
+ local->aql_threshold &&
+ atomic_read(&sta->airtime[txq->ac].aql_tx_pending) <
+ sta->airtime[txq->ac].aql_limit_high)
+ return true;
+
+ return false;
+}
+EXPORT_SYMBOL(ieee80211_txq_airtime_check);
+
bool ieee80211_txq_may_transmit(struct ieee80211_hw *hw,
struct ieee80211_txq *txq)
{
--
2.24.0.rc1.363.gb1bccd3e3d-goog
Kan Yan <[email protected]> writes:
> In order for the Fq_CoDel algorithm integrated in mac80211 layer to operate
> effectively to control excessive queueing latency, the CoDel algorithm
> requires an accurate measure of how long packets stays in the queue, AKA
> sojourn time. The sojourn time measured at the mac80211 layer doesn't
> include queueing latency in the lower layer (firmware/hardware) and CoDel
> expects lower layer to have a short queue. However, most 802.11ac chipsets
> offload tasks such TX aggregation to firmware or hardware, thus have a deep
> lower layer queue.
>
> Without a mechanism to control the lower layer queue size, packets only
> stay in mac80211 layer transiently before being sent to firmware queue.
> As a result, the sojourn time measured by CoDel in the mac80211 layer is
> almost always lower than the CoDel latency target, hence CoDel does little
> to control the latency, even when the lower layer queue causes excessive
> latency.
>
> The Byte Queue Limits (BQL) mechanism is commonly used to address the
> similar issue with wired network interface. However, this method cannot be
> applied directly to the wireless network interface. "Bytes" is not a
> suitable measure of queue depth in the wireless network, as the data rate
> can vary dramatically from station to station in the same network, from a
> few Mbps to over Gbps.
>
> This patch implements an Airtime-based Queue Limit (AQL) to make CoDel work
> effectively with wireless drivers that utilized firmware/hardware
> offloading. AQL allows each txq to release just enough packets to the lower
> layer to form 1-2 large aggregations to keep hardware fully utilized and
> retains the rest of the frames in mac80211 layer to be controlled by the
> CoDel algorithm.
>
> Signed-off-by: Kan Yan <[email protected]>
> [ Toke: Keep API to set pending airtime internal, fix nits in commit msg ]
> Signed-off-by: Toke Høiland-Jørgensen <[email protected]>
Thanks for the update! A few comments below. I'll also send you and
updated version of my patch following this one, with fixes for Johannes'
comments. You can include that in your next version...
> ---
> include/net/cfg80211.h | 7 ++++
> include/net/mac80211.h | 12 ++++++
> net/mac80211/debugfs.c | 78 ++++++++++++++++++++++++++++++++++++++
> net/mac80211/debugfs_sta.c | 43 ++++++++++++++++-----
> net/mac80211/ieee80211_i.h | 4 ++
> net/mac80211/main.c | 10 ++++-
> net/mac80211/sta_info.c | 40 +++++++++++++++++++
> net/mac80211/sta_info.h | 8 ++++
> net/mac80211/tx.c | 47 +++++++++++++++++++++--
> 9 files changed, 235 insertions(+), 14 deletions(-)
>
> diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
> index 4ab2c49423dc..15f9f04de149 100644
> --- a/include/net/cfg80211.h
> +++ b/include/net/cfg80211.h
> @@ -2602,6 +2602,13 @@ enum wiphy_params_flags {
>
> #define IEEE80211_DEFAULT_AIRTIME_WEIGHT 256
>
> +/* The per TXQ device queue limit in airtime */
> +#define IEEE80211_DEFAULT_AQL_TXQ_LIMIT_L 4000
> +#define IEEE80211_DEFAULT_AQL_TXQ_LIMIT_H 8000
> +
> +/* The per interface airtime threshold to switch to lower queue limit */
> +#define IEEE80211_AQL_THRESHOLD 24000
> +
> /**
> * struct cfg80211_pmksa - PMK Security Association
> *
> diff --git a/include/net/mac80211.h b/include/net/mac80211.h
> index 4319596ef472..269be699e89c 100644
> --- a/include/net/mac80211.h
> +++ b/include/net/mac80211.h
> @@ -5558,6 +5558,18 @@ void ieee80211_send_eosp_nullfunc(struct ieee80211_sta *pubsta, int tid);
> void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
> u32 tx_airtime, u32 rx_airtime);
>
> +/**
> + * ieee80211_txq_airtime_check - check if a txq can send frame to device
> + *
> + * @hw: pointer obtained from ieee80211_alloc_hw()
> + * @txq: pointer obtained from station or virtual interface
> + *
> + * Return true if the AQL's airtime limit has not been reached and the txq can
> + * continue to send more packets to the device. Otherwise return false.
> + */
> +bool
> +ieee80211_txq_airtime_check(struct ieee80211_hw *hw, struct ieee80211_txq *txq);
> +
> /**
> * ieee80211_iter_keys - iterate keys programmed into the device
> * @hw: pointer obtained from ieee80211_alloc_hw()
> diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
> index 568b3b276931..d77ea0e51c1d 100644
> --- a/net/mac80211/debugfs.c
> +++ b/net/mac80211/debugfs.c
> @@ -148,6 +148,80 @@ static const struct file_operations aqm_ops = {
> .llseek = default_llseek,
> };
>
> +static ssize_t aql_txq_limit_read(struct file *file,
> + char __user *user_buf,
> + size_t count,
> + loff_t *ppos)
> +{
> + struct ieee80211_local *local = file->private_data;
> + char buf[400];
> + int len = 0;
> +
> + len = scnprintf(buf, sizeof(buf),
> + "AC AQL limit low AQL limit high\n"
> + "VO %u %u\n"
> + "VI %u %u\n"
> + "BE %u %u\n"
> + "BK %u %u\n",
> + local->aql_txq_limit_low[IEEE80211_AC_VO],
> + local->aql_txq_limit_high[IEEE80211_AC_VO],
> + local->aql_txq_limit_low[IEEE80211_AC_VI],
> + local->aql_txq_limit_high[IEEE80211_AC_VI],
> + local->aql_txq_limit_low[IEEE80211_AC_BE],
> + local->aql_txq_limit_high[IEEE80211_AC_BE],
> + local->aql_txq_limit_low[IEEE80211_AC_BK],
> + local->aql_txq_limit_high[IEEE80211_AC_BK]);
> + return simple_read_from_buffer(user_buf, count, ppos,
> + buf, len);
> +}
> +
> +static ssize_t aql_txq_limit_write(struct file *file,
> + const char __user *user_buf,
> + size_t count,
> + loff_t *ppos)
> +{
> + struct ieee80211_local *local = file->private_data;
> + char buf[100];
> + size_t len;
> + u32 ac, q_limit_low, q_limit_high;
> + struct sta_info *sta;
> +
> + if (count > sizeof(buf))
> + return -EINVAL;
> +
> + if (copy_from_user(buf, user_buf, count))
> + return -EFAULT;
> +
> + buf[sizeof(buf) - 1] = 0;
> + len = strlen(buf);
> + if (len > 0 && buf[len - 1] == '\n')
> + buf[len - 1] = 0;
> +
> + if (sscanf(buf, "%u %u %u", &ac, &q_limit_low, &q_limit_high) != 3)
> + return -EINVAL;
> +
> + if (ac >= IEEE80211_NUM_ACS)
> + return -EINVAL;
> +
> + local->aql_txq_limit_low[ac] = q_limit_low;
> + local->aql_txq_limit_high[ac] = q_limit_high;
> +
> + mutex_lock(&local->sta_mtx);
> + list_for_each_entry(sta, &local->sta_list, list) {
> + sta->airtime[ac].aql_limit_low = q_limit_low;
> + sta->airtime[ac].aql_limit_high = q_limit_high;
> + }
Why is this setting sta and device limits to the same value?
Also, are you sure we won't risk write tearing when writing 32-bit
values without locking on some architectures?
> + mutex_unlock(&local->sta_mtx);
> + return count;
> +}
> +
> +static const struct file_operations aql_txq_limit_ops = {
> + .write = aql_txq_limit_write,
> + .read = aql_txq_limit_read,
> + .open = simple_open,
> + .llseek = default_llseek,
> +};
> +
> static ssize_t force_tx_status_read(struct file *file,
> char __user *user_buf,
> size_t count,
> @@ -441,6 +515,10 @@ void debugfs_hw_add(struct ieee80211_local *local)
> debugfs_create_u16("airtime_flags", 0600,
> phyd, &local->airtime_flags);
>
> + DEBUGFS_ADD(aql_txq_limit);
> + debugfs_create_u32("aql_threshold", 0600,
> + phyd, &local->aql_threshold);
> +
> statsd = debugfs_create_dir("statistics", phyd);
>
> /* if the dir failed, don't put all the other things into the root! */
> diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
> index c8ad20c28c43..0185e6e5e5d1 100644
> --- a/net/mac80211/debugfs_sta.c
> +++ b/net/mac80211/debugfs_sta.c
> @@ -197,10 +197,12 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
> {
> struct sta_info *sta = file->private_data;
> struct ieee80211_local *local = sta->sdata->local;
> - size_t bufsz = 200;
> + size_t bufsz = 400;
> char *buf = kzalloc(bufsz, GFP_KERNEL), *p = buf;
> u64 rx_airtime = 0, tx_airtime = 0;
> s64 deficit[IEEE80211_NUM_ACS];
> + u32 q_depth[IEEE80211_NUM_ACS];
> + u32 q_limit_l[IEEE80211_NUM_ACS], q_limit_h[IEEE80211_NUM_ACS];
> ssize_t rv;
> int ac;
>
> @@ -212,19 +214,22 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
> rx_airtime += sta->airtime[ac].rx_airtime;
> tx_airtime += sta->airtime[ac].tx_airtime;
> deficit[ac] = sta->airtime[ac].deficit;
> + q_limit_l[ac] = sta->airtime[ac].aql_limit_low;
> + q_limit_h[ac] = sta->airtime[ac].aql_limit_high;
> spin_unlock_bh(&local->active_txq_lock[ac]);
> + q_depth[ac] = atomic_read(&sta->airtime[ac].aql_tx_pending);
> }
>
> p += scnprintf(p, bufsz + buf - p,
> "RX: %llu us\nTX: %llu us\nWeight: %u\n"
> - "Deficit: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n",
> - rx_airtime,
> - tx_airtime,
> - sta->airtime_weight,
> - deficit[0],
> - deficit[1],
> - deficit[2],
> - deficit[3]);
> + "Deficit: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n"
> + "Q depth: VO: %u us VI: %u us BE: %u us BK: %u us\n"
> + "Q limit[low/high]: VO: %u/%u VI: %u/%u BE: %u/%u BK: %u/%u\n",
> + rx_airtime, tx_airtime, sta->airtime_weight,
> + deficit[0], deficit[1], deficit[2], deficit[3],
> + q_depth[0], q_depth[1], q_depth[2], q_depth[3],
> + q_limit_l[0], q_limit_h[0], q_limit_l[1], q_limit_h[1],
> + q_limit_l[2], q_limit_h[2], q_limit_l[3], q_limit_h[3]),
>
> rv = simple_read_from_buffer(userbuf, count, ppos, buf, p - buf);
> kfree(buf);
> @@ -236,7 +241,25 @@ static ssize_t sta_airtime_write(struct file *file, const char __user *userbuf,
> {
> struct sta_info *sta = file->private_data;
> struct ieee80211_local *local = sta->sdata->local;
> - int ac;
> + u32 ac, q_limit_l, q_limit_h;
> + char _buf[100] = {}, *buf = _buf;
> +
> + if (count > sizeof(_buf))
> + return -EINVAL;
> +
> + if (copy_from_user(buf, userbuf, count))
> + return -EFAULT;
> +
> + buf[sizeof(_buf) - 1] = '\0';
> + if (sscanf(buf, "queue limit %u %u %u", &ac, &q_limit_l, &q_limit_h)
> + != 3)
> + return -EINVAL;
> +
> + if (ac >= IEEE80211_NUM_ACS)
> + return -EINVAL;
> +
> + sta->airtime[ac].aql_limit_low = q_limit_l;
> + sta->airtime[ac].aql_limit_high = q_limit_h;
Same concern as above re: unprotected writes.
> for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
> spin_lock_bh(&local->active_txq_lock[ac]);
> diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
> index 225ea4e3cd76..ad15b3be8bb3 100644
> --- a/net/mac80211/ieee80211_i.h
> +++ b/net/mac80211/ieee80211_i.h
> @@ -1142,6 +1142,10 @@ struct ieee80211_local {
> u16 schedule_round[IEEE80211_NUM_ACS];
>
> u16 airtime_flags;
> + u32 aql_txq_limit_low[IEEE80211_NUM_ACS];
> + u32 aql_txq_limit_high[IEEE80211_NUM_ACS];
> + u32 aql_threshold;
> + atomic_t aql_total_pending_airtime;
>
> const struct ieee80211_ops *ops;
>
> diff --git a/net/mac80211/main.c b/net/mac80211/main.c
> index aba094b4ccfc..071ea92a3748 100644
> --- a/net/mac80211/main.c
> +++ b/net/mac80211/main.c
> @@ -667,8 +667,16 @@ struct ieee80211_hw *ieee80211_alloc_hw_nm(size_t priv_data_len,
> for (i = 0; i < IEEE80211_NUM_ACS; i++) {
> INIT_LIST_HEAD(&local->active_txqs[i]);
> spin_lock_init(&local->active_txq_lock[i]);
> + local->aql_txq_limit_low[i] = IEEE80211_DEFAULT_AQL_TXQ_LIMIT_L;
> + local->aql_txq_limit_high[i] =
> + IEEE80211_DEFAULT_AQL_TXQ_LIMIT_H;
> }
> - local->airtime_flags = AIRTIME_USE_TX | AIRTIME_USE_RX;
> +
> + local->airtime_flags = AIRTIME_USE_TX |
> + AIRTIME_USE_RX |
> + AIRTIME_USE_AQL;
> + local->aql_threshold = IEEE80211_AQL_THRESHOLD;
> + atomic_set(&local->aql_total_pending_airtime, 0);
>
> INIT_LIST_HEAD(&local->chanctx_list);
> mutex_init(&local->chanctx_mtx);
> diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
> index bd11fef2139f..a76e935a543a 100644
> --- a/net/mac80211/sta_info.c
> +++ b/net/mac80211/sta_info.c
> @@ -396,6 +396,9 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
> skb_queue_head_init(&sta->ps_tx_buf[i]);
> skb_queue_head_init(&sta->tx_filtered[i]);
> sta->airtime[i].deficit = sta->airtime_weight;
> + atomic_set(&sta->airtime[i].aql_tx_pending, 0);
> + sta->airtime[i].aql_limit_low = local->aql_txq_limit_low[i];
> + sta->airtime[i].aql_limit_high = local->aql_txq_limit_high[i];
> }
>
> for (i = 0; i < IEEE80211_NUM_TIDS; i++)
> @@ -1893,6 +1896,43 @@ void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
> }
> EXPORT_SYMBOL(ieee80211_sta_register_airtime);
>
> +void ieee80211_sta_update_pending_airtime(struct ieee80211_local *local,
> + struct sta_info *sta, u8 ac,
> + u16 tx_airtime, bool tx_completed)
> +{
> + if (!tx_completed) {
> + if (sta)
> + atomic_add(tx_airtime,
> + &sta->airtime[ac].aql_tx_pending);
> +
> + atomic_add(tx_airtime, &local->aql_total_pending_airtime);
> + return;
> + }
> +
> + if (sta) {
> + if (WARN_ONCE(atomic_read(&sta->airtime[ac].aql_tx_pending) <
> + tx_airtime,
> + "STA %pM AC %d txq pending airtime underflow: %u, %u",
> + sta->addr, ac,
> + atomic_read(&sta->airtime[ac].aql_tx_pending),
> + tx_airtime))
> + atomic_set(&sta->airtime[ac].aql_tx_pending, 0);
I don't think this is right; another thread could do atomic_inc()
between the atomic_read() and atomic_set() here, in which case this
would clobber the other value.
I think to get this right the logic would need to be something like
this:
retry:
old = atomic_read(&sta->airtime[ac].aql_tx_pending);
if (warn_once(tx_airtime > old))
new = 0;
else
new = old - tx_airtime;
if (atomic_cmpxchg(&sta->airtime[ac].aql_tx_pending, old, new) != old)
goto retry;
(or use an equivalent do/while).
-Toke
Thanks for the review. I will pick up your new patches and give it a
try tomorrow.
> Why is this setting sta and device limits to the same value?
local->aql_txq_limit_low is not the per device limit, but the default
txq_limit for all STAs. Individual stations can be configured with
non-default value via debugfs entry
"netdev:interface_name_x/stations/mac_addr_x/airtime". "aql_threshold"
is the device limit for switching between the lower and higher per
station queue limit.
> Also, are you sure we won't risk write tearing when writing 32-bit
> values without locking on some architectures?
Does mac80211 ever runs in any 16-bit architectures? Even in an
architecture that write to 32-bit value is not atomic, I don't think
there is any side-effect for queue limit get wrong transiently in rare
occasions. Besides, the practical value of those queue limits should
always fit into 16 bits.
> I don't think this is right; another thread could do atomic_inc()
> between the atomic_read() and atomic_set() here, in which case this
> would clobber the other value.
> I think to get this right the logic would need to be something like
> this:
> retry:
> old = atomic_read(&sta->airtime[ac].aql_tx_pending);
> if (warn_once(tx_airtime > old))
> new = 0;
> else
> new = old - tx_airtime;
> if (atomic_cmpxchg(&sta->airtime[ac].aql_tx_pending, old, new) != old)
> goto retry;
> (or use an equivalent do/while).
That's indeed not right. However, if a potential aql_tx_pending
underflow case is detected here (It should never happen), reset it to
0 maybe not the best remedy anyway. I think it is better just
WARN_ONCE() and skip updating aql_tx_pending all together, so the
retry or loop can be avoided here. What do you think?
On Tue, Nov 12, 2019 at 3:48 AM Toke Høiland-Jørgensen <[email protected]> wrote:
>
> Kan Yan <[email protected]> writes:
>
> > In order for the Fq_CoDel algorithm integrated in mac80211 layer to operate
> > effectively to control excessive queueing latency, the CoDel algorithm
> > requires an accurate measure of how long packets stays in the queue, AKA
> > sojourn time. The sojourn time measured at the mac80211 layer doesn't
> > include queueing latency in the lower layer (firmware/hardware) and CoDel
> > expects lower layer to have a short queue. However, most 802.11ac chipsets
> > offload tasks such TX aggregation to firmware or hardware, thus have a deep
> > lower layer queue.
> >
> > Without a mechanism to control the lower layer queue size, packets only
> > stay in mac80211 layer transiently before being sent to firmware queue.
> > As a result, the sojourn time measured by CoDel in the mac80211 layer is
> > almost always lower than the CoDel latency target, hence CoDel does little
> > to control the latency, even when the lower layer queue causes excessive
> > latency.
> >
> > The Byte Queue Limits (BQL) mechanism is commonly used to address the
> > similar issue with wired network interface. However, this method cannot be
> > applied directly to the wireless network interface. "Bytes" is not a
> > suitable measure of queue depth in the wireless network, as the data rate
> > can vary dramatically from station to station in the same network, from a
> > few Mbps to over Gbps.
> >
> > This patch implements an Airtime-based Queue Limit (AQL) to make CoDel work
> > effectively with wireless drivers that utilized firmware/hardware
> > offloading. AQL allows each txq to release just enough packets to the lower
> > layer to form 1-2 large aggregations to keep hardware fully utilized and
> > retains the rest of the frames in mac80211 layer to be controlled by the
> > CoDel algorithm.
> >
> > Signed-off-by: Kan Yan <[email protected]>
> > [ Toke: Keep API to set pending airtime internal, fix nits in commit msg ]
> > Signed-off-by: Toke Høiland-Jørgensen <[email protected]>
>
> Thanks for the update! A few comments below. I'll also send you and
> updated version of my patch following this one, with fixes for Johannes'
> comments. You can include that in your next version...
>
> > ---
> > include/net/cfg80211.h | 7 ++++
> > include/net/mac80211.h | 12 ++++++
> > net/mac80211/debugfs.c | 78 ++++++++++++++++++++++++++++++++++++++
> > net/mac80211/debugfs_sta.c | 43 ++++++++++++++++-----
> > net/mac80211/ieee80211_i.h | 4 ++
> > net/mac80211/main.c | 10 ++++-
> > net/mac80211/sta_info.c | 40 +++++++++++++++++++
> > net/mac80211/sta_info.h | 8 ++++
> > net/mac80211/tx.c | 47 +++++++++++++++++++++--
> > 9 files changed, 235 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
> > index 4ab2c49423dc..15f9f04de149 100644
> > --- a/include/net/cfg80211.h
> > +++ b/include/net/cfg80211.h
> > @@ -2602,6 +2602,13 @@ enum wiphy_params_flags {
> >
> > #define IEEE80211_DEFAULT_AIRTIME_WEIGHT 256
> >
> > +/* The per TXQ device queue limit in airtime */
> > +#define IEEE80211_DEFAULT_AQL_TXQ_LIMIT_L 4000
> > +#define IEEE80211_DEFAULT_AQL_TXQ_LIMIT_H 8000
> > +
> > +/* The per interface airtime threshold to switch to lower queue limit */
> > +#define IEEE80211_AQL_THRESHOLD 24000
> > +
> > /**
> > * struct cfg80211_pmksa - PMK Security Association
> > *
> > diff --git a/include/net/mac80211.h b/include/net/mac80211.h
> > index 4319596ef472..269be699e89c 100644
> > --- a/include/net/mac80211.h
> > +++ b/include/net/mac80211.h
> > @@ -5558,6 +5558,18 @@ void ieee80211_send_eosp_nullfunc(struct ieee80211_sta *pubsta, int tid);
> > void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
> > u32 tx_airtime, u32 rx_airtime);
> >
> > +/**
> > + * ieee80211_txq_airtime_check - check if a txq can send frame to device
> > + *
> > + * @hw: pointer obtained from ieee80211_alloc_hw()
> > + * @txq: pointer obtained from station or virtual interface
> > + *
> > + * Return true if the AQL's airtime limit has not been reached and the txq can
> > + * continue to send more packets to the device. Otherwise return false.
> > + */
> > +bool
> > +ieee80211_txq_airtime_check(struct ieee80211_hw *hw, struct ieee80211_txq *txq);
> > +
> > /**
> > * ieee80211_iter_keys - iterate keys programmed into the device
> > * @hw: pointer obtained from ieee80211_alloc_hw()
> > diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
> > index 568b3b276931..d77ea0e51c1d 100644
> > --- a/net/mac80211/debugfs.c
> > +++ b/net/mac80211/debugfs.c
> > @@ -148,6 +148,80 @@ static const struct file_operations aqm_ops = {
> > .llseek = default_llseek,
> > };
> >
> > +static ssize_t aql_txq_limit_read(struct file *file,
> > + char __user *user_buf,
> > + size_t count,
> > + loff_t *ppos)
> > +{
> > + struct ieee80211_local *local = file->private_data;
> > + char buf[400];
> > + int len = 0;
> > +
> > + len = scnprintf(buf, sizeof(buf),
> > + "AC AQL limit low AQL limit high\n"
> > + "VO %u %u\n"
> > + "VI %u %u\n"
> > + "BE %u %u\n"
> > + "BK %u %u\n",
> > + local->aql_txq_limit_low[IEEE80211_AC_VO],
> > + local->aql_txq_limit_high[IEEE80211_AC_VO],
> > + local->aql_txq_limit_low[IEEE80211_AC_VI],
> > + local->aql_txq_limit_high[IEEE80211_AC_VI],
> > + local->aql_txq_limit_low[IEEE80211_AC_BE],
> > + local->aql_txq_limit_high[IEEE80211_AC_BE],
> > + local->aql_txq_limit_low[IEEE80211_AC_BK],
> > + local->aql_txq_limit_high[IEEE80211_AC_BK]);
> > + return simple_read_from_buffer(user_buf, count, ppos,
> > + buf, len);
> > +}
> > +
> > +static ssize_t aql_txq_limit_write(struct file *file,
> > + const char __user *user_buf,
> > + size_t count,
> > + loff_t *ppos)
> > +{
> > + struct ieee80211_local *local = file->private_data;
> > + char buf[100];
> > + size_t len;
> > + u32 ac, q_limit_low, q_limit_high;
> > + struct sta_info *sta;
> > +
> > + if (count > sizeof(buf))
> > + return -EINVAL;
> > +
> > + if (copy_from_user(buf, user_buf, count))
> > + return -EFAULT;
> > +
> > + buf[sizeof(buf) - 1] = 0;
> > + len = strlen(buf);
> > + if (len > 0 && buf[len - 1] == '\n')
> > + buf[len - 1] = 0;
> > +
> > + if (sscanf(buf, "%u %u %u", &ac, &q_limit_low, &q_limit_high) != 3)
> > + return -EINVAL;
> > +
> > + if (ac >= IEEE80211_NUM_ACS)
> > + return -EINVAL;
> > +
> > + local->aql_txq_limit_low[ac] = q_limit_low;
> > + local->aql_txq_limit_high[ac] = q_limit_high;
> > +
> > + mutex_lock(&local->sta_mtx);
> > + list_for_each_entry(sta, &local->sta_list, list) {
> > + sta->airtime[ac].aql_limit_low = q_limit_low;
> > + sta->airtime[ac].aql_limit_high = q_limit_high;
> > + }
>
> Why is this setting sta and device limits to the same value?
>
> Also, are you sure we won't risk write tearing when writing 32-bit
> values without locking on some architectures?
>
> > + mutex_unlock(&local->sta_mtx);
> > + return count;
> > +}
> > +
> > +static const struct file_operations aql_txq_limit_ops = {
> > + .write = aql_txq_limit_write,
> > + .read = aql_txq_limit_read,
> > + .open = simple_open,
> > + .llseek = default_llseek,
> > +};
> > +
> > static ssize_t force_tx_status_read(struct file *file,
> > char __user *user_buf,
> > size_t count,
> > @@ -441,6 +515,10 @@ void debugfs_hw_add(struct ieee80211_local *local)
> > debugfs_create_u16("airtime_flags", 0600,
> > phyd, &local->airtime_flags);
> >
> > + DEBUGFS_ADD(aql_txq_limit);
> > + debugfs_create_u32("aql_threshold", 0600,
> > + phyd, &local->aql_threshold);
> > +
> > statsd = debugfs_create_dir("statistics", phyd);
> >
> > /* if the dir failed, don't put all the other things into the root! */
> > diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
> > index c8ad20c28c43..0185e6e5e5d1 100644
> > --- a/net/mac80211/debugfs_sta.c
> > +++ b/net/mac80211/debugfs_sta.c
> > @@ -197,10 +197,12 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
> > {
> > struct sta_info *sta = file->private_data;
> > struct ieee80211_local *local = sta->sdata->local;
> > - size_t bufsz = 200;
> > + size_t bufsz = 400;
> > char *buf = kzalloc(bufsz, GFP_KERNEL), *p = buf;
> > u64 rx_airtime = 0, tx_airtime = 0;
> > s64 deficit[IEEE80211_NUM_ACS];
> > + u32 q_depth[IEEE80211_NUM_ACS];
> > + u32 q_limit_l[IEEE80211_NUM_ACS], q_limit_h[IEEE80211_NUM_ACS];
> > ssize_t rv;
> > int ac;
> >
> > @@ -212,19 +214,22 @@ static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
> > rx_airtime += sta->airtime[ac].rx_airtime;
> > tx_airtime += sta->airtime[ac].tx_airtime;
> > deficit[ac] = sta->airtime[ac].deficit;
> > + q_limit_l[ac] = sta->airtime[ac].aql_limit_low;
> > + q_limit_h[ac] = sta->airtime[ac].aql_limit_high;
> > spin_unlock_bh(&local->active_txq_lock[ac]);
> > + q_depth[ac] = atomic_read(&sta->airtime[ac].aql_tx_pending);
> > }
> >
> > p += scnprintf(p, bufsz + buf - p,
> > "RX: %llu us\nTX: %llu us\nWeight: %u\n"
> > - "Deficit: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n",
> > - rx_airtime,
> > - tx_airtime,
> > - sta->airtime_weight,
> > - deficit[0],
> > - deficit[1],
> > - deficit[2],
> > - deficit[3]);
> > + "Deficit: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n"
> > + "Q depth: VO: %u us VI: %u us BE: %u us BK: %u us\n"
> > + "Q limit[low/high]: VO: %u/%u VI: %u/%u BE: %u/%u BK: %u/%u\n",
> > + rx_airtime, tx_airtime, sta->airtime_weight,
> > + deficit[0], deficit[1], deficit[2], deficit[3],
> > + q_depth[0], q_depth[1], q_depth[2], q_depth[3],
> > + q_limit_l[0], q_limit_h[0], q_limit_l[1], q_limit_h[1],
> > + q_limit_l[2], q_limit_h[2], q_limit_l[3], q_limit_h[3]),
> >
> > rv = simple_read_from_buffer(userbuf, count, ppos, buf, p - buf);
> > kfree(buf);
> > @@ -236,7 +241,25 @@ static ssize_t sta_airtime_write(struct file *file, const char __user *userbuf,
> > {
> > struct sta_info *sta = file->private_data;
> > struct ieee80211_local *local = sta->sdata->local;
> > - int ac;
> > + u32 ac, q_limit_l, q_limit_h;
> > + char _buf[100] = {}, *buf = _buf;
> > +
> > + if (count > sizeof(_buf))
> > + return -EINVAL;
> > +
> > + if (copy_from_user(buf, userbuf, count))
> > + return -EFAULT;
> > +
> > + buf[sizeof(_buf) - 1] = '\0';
> > + if (sscanf(buf, "queue limit %u %u %u", &ac, &q_limit_l, &q_limit_h)
> > + != 3)
> > + return -EINVAL;
> > +
> > + if (ac >= IEEE80211_NUM_ACS)
> > + return -EINVAL;
> > +
> > + sta->airtime[ac].aql_limit_low = q_limit_l;
> > + sta->airtime[ac].aql_limit_high = q_limit_h;
>
> Same concern as above re: unprotected writes.
>
> > for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
> > spin_lock_bh(&local->active_txq_lock[ac]);
> > diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
> > index 225ea4e3cd76..ad15b3be8bb3 100644
> > --- a/net/mac80211/ieee80211_i.h
> > +++ b/net/mac80211/ieee80211_i.h
> > @@ -1142,6 +1142,10 @@ struct ieee80211_local {
> > u16 schedule_round[IEEE80211_NUM_ACS];
> >
> > u16 airtime_flags;
> > + u32 aql_txq_limit_low[IEEE80211_NUM_ACS];
> > + u32 aql_txq_limit_high[IEEE80211_NUM_ACS];
> > + u32 aql_threshold;
> > + atomic_t aql_total_pending_airtime;
> >
> > const struct ieee80211_ops *ops;
> >
> > diff --git a/net/mac80211/main.c b/net/mac80211/main.c
> > index aba094b4ccfc..071ea92a3748 100644
> > --- a/net/mac80211/main.c
> > +++ b/net/mac80211/main.c
> > @@ -667,8 +667,16 @@ struct ieee80211_hw *ieee80211_alloc_hw_nm(size_t priv_data_len,
> > for (i = 0; i < IEEE80211_NUM_ACS; i++) {
> > INIT_LIST_HEAD(&local->active_txqs[i]);
> > spin_lock_init(&local->active_txq_lock[i]);
> > + local->aql_txq_limit_low[i] = IEEE80211_DEFAULT_AQL_TXQ_LIMIT_L;
> > + local->aql_txq_limit_high[i] =
> > + IEEE80211_DEFAULT_AQL_TXQ_LIMIT_H;
> > }
> > - local->airtime_flags = AIRTIME_USE_TX | AIRTIME_USE_RX;
> > +
> > + local->airtime_flags = AIRTIME_USE_TX |
> > + AIRTIME_USE_RX |
> > + AIRTIME_USE_AQL;
> > + local->aql_threshold = IEEE80211_AQL_THRESHOLD;
> > + atomic_set(&local->aql_total_pending_airtime, 0);
> >
> > INIT_LIST_HEAD(&local->chanctx_list);
> > mutex_init(&local->chanctx_mtx);
> > diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
> > index bd11fef2139f..a76e935a543a 100644
> > --- a/net/mac80211/sta_info.c
> > +++ b/net/mac80211/sta_info.c
> > @@ -396,6 +396,9 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
> > skb_queue_head_init(&sta->ps_tx_buf[i]);
> > skb_queue_head_init(&sta->tx_filtered[i]);
> > sta->airtime[i].deficit = sta->airtime_weight;
> > + atomic_set(&sta->airtime[i].aql_tx_pending, 0);
> > + sta->airtime[i].aql_limit_low = local->aql_txq_limit_low[i];
> > + sta->airtime[i].aql_limit_high = local->aql_txq_limit_high[i];
> > }
> >
> > for (i = 0; i < IEEE80211_NUM_TIDS; i++)
> > @@ -1893,6 +1896,43 @@ void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
> > }
> > EXPORT_SYMBOL(ieee80211_sta_register_airtime);
> >
> > +void ieee80211_sta_update_pending_airtime(struct ieee80211_local *local,
> > + struct sta_info *sta, u8 ac,
> > + u16 tx_airtime, bool tx_completed)
> > +{
> > + if (!tx_completed) {
> > + if (sta)
> > + atomic_add(tx_airtime,
> > + &sta->airtime[ac].aql_tx_pending);
> > +
> > + atomic_add(tx_airtime, &local->aql_total_pending_airtime);
> > + return;
> > + }
> > +
> > + if (sta) {
> > + if (WARN_ONCE(atomic_read(&sta->airtime[ac].aql_tx_pending) <
> > + tx_airtime,
> > + "STA %pM AC %d txq pending airtime underflow: %u, %u",
> > + sta->addr, ac,
> > + atomic_read(&sta->airtime[ac].aql_tx_pending),
> > + tx_airtime))
> > + atomic_set(&sta->airtime[ac].aql_tx_pending, 0);
>
> I don't think this is right; another thread could do atomic_inc()
> between the atomic_read() and atomic_set() here, in which case this
> would clobber the other value.
>
> I think to get this right the logic would need to be something like
> this:
>
> retry:
> old = atomic_read(&sta->airtime[ac].aql_tx_pending);
> if (warn_once(tx_airtime > old))
> new = 0;
> else
> new = old - tx_airtime;
>
> if (atomic_cmpxchg(&sta->airtime[ac].aql_tx_pending, old, new) != old)
> goto retry;
>
>
> (or use an equivalent do/while).
>
>
> -Toke
>
Kan Yan <[email protected]> writes:
> Thanks for the review. I will pick up your new patches and give it a
> try tomorrow.
>
>> Why is this setting sta and device limits to the same value?
>
> local->aql_txq_limit_low is not the per device limit, but the default
> txq_limit for all STAs. Individual stations can be configured with
> non-default value via debugfs entry
> "netdev:interface_name_x/stations/mac_addr_x/airtime". "aql_threshold"
> is the device limit for switching between the lower and higher per
> station queue limit.
Oh, right, I see. But in that case, should writing the default really
stomp on all the per-station values? If I set the value of a station, I
wouldn't expect it to change just because I changed the default value
afterwards?
>> Also, are you sure we won't risk write tearing when writing 32-bit
>> values without locking on some architectures?
>
> Does mac80211 ever runs in any 16-bit architectures? Even in an
> architecture that write to 32-bit value is not atomic, I don't think
> there is any side-effect for queue limit get wrong transiently in rare
> occasions. Besides, the practical value of those queue limits should
> always fit into 16 bits.
I'm not sure about the platform characteristics of all the weird tiny
MIPS boxes that run OpenWrt; which is why I'm vary of making any
assumptions that it is safe :)
But yeah, I suppose you're right that since we're just setting the
limit, it is not going to be a huge concern here...
>> I don't think this is right; another thread could do atomic_inc()
>> between the atomic_read() and atomic_set() here, in which case this
>> would clobber the other value.
>> I think to get this right the logic would need to be something like
>> this:
>> retry:
>> old = atomic_read(&sta->airtime[ac].aql_tx_pending);
>> if (warn_once(tx_airtime > old))
>> new = 0;
>> else
>> new = old - tx_airtime;
>> if (atomic_cmpxchg(&sta->airtime[ac].aql_tx_pending, old, new) != old)
>> goto retry;
>> (or use an equivalent do/while).
>
> That's indeed not right. However, if a potential aql_tx_pending
> underflow case is detected here (It should never happen), reset it to
> 0 maybe not the best remedy anyway. I think it is better just
> WARN_ONCE() and skip updating aql_tx_pending all together, so the
> retry or loop can be avoided here. What do you think?
If we don't reset the value to zero may end up with a device that is
unable to transmit. Better to reset it I think, even if this is never
supposed to happen...
-Toke
> Oh, right, I see. But in that case, should writing the default really
> stomp on all the per-station values? If I set the value of a station, I
> wouldn't expect it to change just because I changed the default value
> afterwards?
Will persevere the value for stations with customized queue limit in
the next version.
> > That's indeed not right. However, if a potential aql_tx_pending
> > underflow case is detected here (It should never happen), reset it to
> > 0 maybe not the best remedy anyway. I think it is better just
> > WARN_ONCE() and skip updating aql_tx_pending all together, so the
> > retry or loop can be avoided here. What do you think?
> If we don't reset the value to zero may end up with a device that is
> unable to transmit. Better to reset it I think, even if this is never
> supposed to happen...
I mean not updating the pending airtime to prevent it from going
negative when the tx_airtime is larger than aql_tx_pending.
Will reset it to 0 in next version, which is simpler and cleaner.
On Wed, Nov 13, 2019 at 6:02 AM Toke Høiland-Jørgensen <[email protected]> wrote:
>
> Kan Yan <[email protected]> writes:
>
> > Thanks for the review. I will pick up your new patches and give it a
> > try tomorrow.
> >
> >> Why is this setting sta and device limits to the same value?
> >
> > local->aql_txq_limit_low is not the per device limit, but the default
> > txq_limit for all STAs. Individual stations can be configured with
> > non-default value via debugfs entry
> > "netdev:interface_name_x/stations/mac_addr_x/airtime". "aql_threshold"
> > is the device limit for switching between the lower and higher per
> > station queue limit.
>
> Oh, right, I see. But in that case, should writing the default really
> stomp on all the per-station values? If I set the value of a station, I
> wouldn't expect it to change just because I changed the default value
> afterwards?
>
> >> Also, are you sure we won't risk write tearing when writing 32-bit
> >> values without locking on some architectures?
> >
> > Does mac80211 ever runs in any 16-bit architectures? Even in an
> > architecture that write to 32-bit value is not atomic, I don't think
> > there is any side-effect for queue limit get wrong transiently in rare
> > occasions. Besides, the practical value of those queue limits should
> > always fit into 16 bits.
>
> I'm not sure about the platform characteristics of all the weird tiny
> MIPS boxes that run OpenWrt; which is why I'm vary of making any
> assumptions that it is safe :)
>
> But yeah, I suppose you're right that since we're just setting the
> limit, it is not going to be a huge concern here...
>
> >> I don't think this is right; another thread could do atomic_inc()
> >> between the atomic_read() and atomic_set() here, in which case this
> >> would clobber the other value.
> >> I think to get this right the logic would need to be something like
> >> this:
> >> retry:
> >> old = atomic_read(&sta->airtime[ac].aql_tx_pending);
> >> if (warn_once(tx_airtime > old))
> >> new = 0;
> >> else
> >> new = old - tx_airtime;
> >> if (atomic_cmpxchg(&sta->airtime[ac].aql_tx_pending, old, new) != old)
> >> goto retry;
> >> (or use an equivalent do/while).
> >
> > That's indeed not right. However, if a potential aql_tx_pending
> > underflow case is detected here (It should never happen), reset it to
> > 0 maybe not the best remedy anyway. I think it is better just
> > WARN_ONCE() and skip updating aql_tx_pending all together, so the
> > retry or loop can be avoided here. What do you think?
>
> If we don't reset the value to zero may end up with a device that is
> unable to transmit. Better to reset it I think, even if this is never
> supposed to happen...
>
> -Toke
>