mac80211: Shrink the size of ack_frame_id to make room for tx_time_est

To implement airtime queue limiting, we need to keep a running account of
the estimated airtime of all skbs queued into the device. Do to this
correctly, we need to store the airtime estimate into the skb so we can
decrease the outstanding balance when the skb is freed. This means that the
time estimate must be stored somewhere that will survive for the lifetime
of the skb.

To get this, decrease the size of the ack_frame_id field to 6 bits, and
lower the size of the ID space accordingly. This leaves 10 bits for use for
tx_time_est, which is enough to store a maximum of 4096 us, if we shift the
values so they become units of 4us.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/157182474063.150713.16132669599100802716.stgit@toke.dk
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index f5996960eaceaa1c2038d82a59dc3de8d18848c3..c643a19dce9614ded5de67939d5169155dac194d 100644 (file)
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -967,6 +967,7 @@ ieee80211_rate_get_vht_nss(const struct ieee80211_tx_rate *rate)
  * @band: the band to transmit on (use for checking for races)
  * @hw_queue: HW queue to put the frame on, skb_get_queue_mapping() gives the AC
  * @ack_frame_id: internal frame ID for TX status, used internally
+ * @tx_time_est: TX time estimate in units of 4us, used internally
  * @control: union part for control data
  * @control.rates: TX rates array to try
  * @control.rts_cts_rate_idx: rate for RTS or CTS
@@ -1007,7 +1008,8 @@ struct ieee80211_tx_info {
 
        u8 hw_queue;
 
-       u16 ack_frame_id;
+       u16 ack_frame_id:6;
+       u16 tx_time_est:10;
 
        union {
                struct {

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 70739e746c13eef86b255f63d4e92a968b036fa4..4fb7f1f1210980df126c0560fd6cc824fc1388c9 100644 (file)
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -3428,7 +3428,7 @@ int ieee80211_attach_ack_skb(struct ieee80211_local *local, struct sk_buff *skb,
 
        spin_lock_irqsave(&local->ack_status_lock, spin_flags);
        id = idr_alloc(&local->ack_status_frames, ack_skb,
-                      1, 0x10000, GFP_ATOMIC);
+                      1, 0x40, GFP_ATOMIC);
        spin_unlock_irqrestore(&local->ack_status_lock, spin_flags);
 
        if (id < 0) {

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index a4c435abe15fd409eb2a68e509176ba3358804b6..db38be1b75fa68efd0a13bd85c773d4d5335d8bd 100644 (file)
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2430,7 +2430,7 @@ static int ieee80211_store_ack_skb(struct ieee80211_local *local,
 
                spin_lock_irqsave(&local->ack_status_lock, flags);
                id = idr_alloc(&local->ack_status_frames, ack_skb,
-                              1, 0x10000, GFP_ATOMIC);
+                              1, 0x40, GFP_ATOMIC);
                spin_unlock_irqrestore(&local->ack_status_lock, flags);
 
                if (id >= 0) {