This patch introduces a PID sharpening factor for faster response on
association and interpolation.
Signed-off-by: Stefano Brivio <stefano.brivio@xxxxxxxxx>
---
Index: wireless-2.6/net/mac80211/rc80211_pid.c
===================================================================
--- wireless-2.6.orig/net/mac80211/rc80211_pid.c
+++ wireless-2.6/net/mac80211/rc80211_pid.c
@@ -23,13 +23,16 @@
*
* The controller basically computes the following:
*
- * adj = CP * err + CI * err_avg + CD * (err - last_err)
+ * adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening)
*
* where
* adj adjustment value that is used to switch TX rate (see below)
* err current error: target vs. current failed frames percentage
* last_err last error
* err_avg average (i.e. poor man's integral) of recent errors
+ * sharpening non-zero when fast response is needed (i.e. right after
+ * association or no frames sent for a long time), heading
+ * to zero over time
* CP Proportional coefficient
* CI Integral coefficient
* CD Derivative coefficient
@@ -65,6 +68,11 @@
#define RC_PID_SMOOTHING_SHIFT 3
#define RC_PID_SMOOTHING (1 << RC_PID_SMOOTHING_SHIFT)
+/* Sharpening factor (used for D part of PID controller) */
+#define RATE_CONTROL_SHARPENING_SHIFT 2
+#define RATE_CONTROL_SHARPENING (1 << RATE_CONTROL_SHARPENING_SHIFT)
+#define RATE_CONTROL_SHARPENING_DURATION 1
+
/* Fixed point arithmetic shifting amount. */
#define RC_PID_ARITH_SHIFT 8
@@ -131,8 +139,11 @@ struct rc_pid_sta_info {
*/
s32 err_avg_sc;
- /* Last framed failes percentage sample */
+ /* Last framed failes percentage sample. */
u32 last_pf;
+
+ /* Sharpening needed. */
+ u8 sharp_cnt;
};
/* Algorithm parameters. We keep them on a per-algorithm approach, so they can
@@ -275,20 +286,26 @@ static void rate_control_pid_sample(stru
mode = local->oper_hw_mode;
spinfo = sta->rate_ctrl_priv;
+
+ /* In case nothing happened during the previous control interval, turn
+ * on the sharpening factor. */
+ if (jiffies - spinfo->last_sample > RC_PID_INTERVAL)
+ spinfo->sharp_cnt = RATE_CONTROL_SHARPENING_DURATION;
+
spinfo->last_sample = jiffies;
- /* If no frames were transmitted, we assume the old sample is
+ /* This should never happen, but in case, we assume the old sample is
* still a good measurement and copy it. */
- if (spinfo->tx_num_xmit == 0)
+ if (unlikely(spinfo->tx_num_xmit == 0))
pf = spinfo->last_pf;
else {
pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
pf <<= RC_PID_ARITH_SHIFT;
-
- spinfo->tx_num_xmit = 0;
- spinfo->tx_num_failed = 0;
}
+ spinfo->tx_num_xmit = 0;
+ spinfo->tx_num_failed = 0;
+
/* If we just switched rate, update the rate behaviour info. */
if (pinfo->oldrate != sta->txrate) {
@@ -313,8 +330,11 @@ static void rate_control_pid_sample(stru
spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
err_int = spinfo->err_avg_sc >> RC_PID_SMOOTHING_SHIFT;
- err_der = pf - spinfo->last_pf;
+ err_der = pf - spinfo->last_pf
+ * (1 + RATE_CONTROL_SHARPENING * spinfo->sharp_cnt);
spinfo->last_pf = pf;
+ if (spinfo->sharp_cnt)
+ spinfo->sharp_cnt--;
/* Compute the controller output. */
adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
--
Ciao
Stefano
-
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