Return-path: Received: from mfe1.polimi.it ([131.175.12.23]:34599 "EHLO polimi.it" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751138AbXLIU1q (ORCPT ); Sun, 9 Dec 2007 15:27:46 -0500 Date: Sun, 9 Dec 2007 21:21:33 +0100 From: Stefano Brivio To: linux-wireless , Mattias Nissler Cc: "John W. Linville" , Johannes Berg Subject: [RFC/T][PATCH 2/3] rc80211-pid: introduce PID sharpening factor Message-ID: <20071209212133.43030d03@morte> (sfid-20071209_202749_864559_C3582E0C) In-Reply-To: <20071209211547.2d7fca32@morte> References: <20071209211547.2d7fca32@morte> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-wireless-owner@vger.kernel.org List-ID: This patch introduces a PID sharpening factor for faster response on association and interpolation. Signed-off-by: Stefano Brivio --- 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 +23,15 @@ * * 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 interpolation), heading to zero over time * CP Proportional coefficient * CI Integral coefficient * CD Derivative coefficient @@ -65,6 +67,11 @@ #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 @@ -127,8 +134,11 @@ 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 @@ -271,10 +281,12 @@ static void rate_control_pid_sample(stru spinfo->last_sample = jiffies; /* If no frames were transmitted, we assume the old sample is - * still a good measurement and copy it. */ - if (spinfo->tx_num_xmit == 0) + * still a good measurement and copy it, and turn the sharpening factor + * on. */ + if (spinfo->tx_num_xmit == 0) { pf = spinfo->last_pf; - else { + spinfo->sharp_cnt = RATE_CONTROL_SHARPENING_DURATION; + } else { pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit; pf <<= RC_PID_ARITH_SHIFT; @@ -314,8 +326,11 @@ 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