Sorry, it looks like I didn't refresh the patch I just inlined:
Index: wireless-2.6/net/mac80211/rc80211_simple.c
===================================================================
--- wireless-2.6.orig/net/mac80211/rc80211_simple.c
+++ wireless-2.6/net/mac80211/rc80211_simple.c
@@ -26,13 +26,15 @@
*
* The controller basically computes the following:
*
- * adj = CP * err + CI * err_avg + CD * (err - last_err)
+ * adj = CP * err + CI * err_avg + CD * (1 + sharpening) * (err - last_err)
*
* 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 interpolation)
* CP Proportional coefficient
* CI Integral coefficient
* CD Derivative coefficient
@@ -62,6 +64,11 @@
#define RATE_CONTROL_SMOOTHING_SHIFT 3
#define RATE_CONTROL_SMOOTHING (1 << RATE_CONTROL_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 3
+
/* Fixed point arithmetic shifting amount. */
#define RATE_CONTROL_ARITH_SHIFT 8
@@ -122,6 +129,9 @@ struct sta_rate_control {
/* Last framed failes percentage sample */
u32 last_pf;
+ /* Sharpening needed */
+ u8 sharp_cnt;
+
unsigned long avg_rate_update;
u32 tx_avg_rate_sum;
u32 tx_avg_rate_num;
@@ -252,11 +262,13 @@ static void rate_control_simple_tx_statu
srctrl->last_sample = jiffies;
/* If no frames were transmitted, we assume the old sample is
- * still a good measurement and copy it.
+ * still a good measurement and copy it, and turn the
+ * sharpening factor on.
*/
- if (srctrl->tx_num_xmit == 0)
+ if (srctrl->tx_num_xmit == 0) {
pf = srctrl->last_pf;
- else {
+ srctrl->sharp_cnt = RATE_CONTROL_SHARPENING_DURATION;
+ } else {
pf = srctrl->tx_num_failed * 100 / srctrl->tx_num_xmit;
pf <<= RATE_CONTROL_ARITH_SHIFT;
@@ -271,8 +283,11 @@ static void rate_control_simple_tx_statu
srctrl->err_avg_sc = srctrl->err_avg_sc - err_avg + err_prop;
err_int = srctrl->err_avg_sc >> RATE_CONTROL_SMOOTHING_SHIFT;
- err_der = pf - srctrl->last_pf;
+ err_der = (pf - srctrl->last_pf) *
+ (1 + RATE_CONTROL_SHARPENING * srctrl->sharp_cnt);
srctrl->last_pf = pf;
+ if (srctrl->sharp_cnt)
+ srctrl->sharp_cnt--;
/* Compute the controller output. */
adj = (err_prop * RATE_CONTROL_COEFF_P
--
Ciao
Stefano
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