Return-path: Received: from mfe1.polimi.it ([131.175.12.23]:57407 "EHLO polimi.it" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751116AbXLCDab (ORCPT ); Sun, 2 Dec 2007 22:30:31 -0500 Date: Mon, 3 Dec 2007 04:26:56 +0100 From: Stefano Brivio To: Stefano Brivio Cc: Mattias Nissler , linux-wireless , "John W. Linville" , Johannes Berg Subject: Re: [RFC][PATCH] mac80211: Use PID controller for TX rate control Message-ID: <20071203042656.1aad7ad6@morte> (sfid-20071203_033112_503688_FCB487EE) In-Reply-To: <20071203041608.3af3b462@morte> References: <1196622331.7472.4.camel@localhost> <20071203041608.3af3b462@morte> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-wireless-owner@vger.kernel.org List-ID: 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