mac80211: add the 'minstrel' rate control algorithm

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 583 insertions, 0 deletions

diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
new file mode 100644
index 000000000000..f6d69dab07a3
--- /dev/null
+++ b/net/mac80211/rc80211_minstrel.c
@@ -0,0 +1,583 @@
+/*
+ * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Based on minstrel.c:
+ *   Copyright (C) 2005-2007 Derek Smithies <derek@indranet.co.nz>
+ *   Sponsored by Indranet Technologies Ltd
+ *
+ * Based on sample.c:
+ *   Copyright (c) 2005 John Bicket
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer,
+ *      without modification.
+ *   2. Redistributions in binary form must reproduce at minimum a disclaimer
+ *      similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any
+ *      redistribution must be conditioned upon including a substantially
+ *      similar Disclaimer requirement for further binary redistribution.
+ *   3. Neither the names of the above-listed copyright holders nor the names
+ *      of any contributors may be used to endorse or promote products derived
+ *      from this software without specific prior written permission.
+ *
+ *   Alternatively, this software may be distributed under the terms of the
+ *   GNU General Public License ("GPL") version 2 as published by the Free
+ *   Software Foundation.
+ *
+ *   NO WARRANTY
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF NONINFRINGEMENT, MERCHANTIBILITY
+ *   AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+ *   THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY,
+ *   OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *   SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+ *   IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ *   THE POSSIBILITY OF SUCH DAMAGES.
+ */
+#include <linux/netdevice.h>
+#include <linux/types.h>
+#include <linux/skbuff.h>
+#include <linux/debugfs.h>
+#include <linux/random.h>
+#include <linux/ieee80211.h>
+#include <net/mac80211.h>
+#include "rate.h"
+#include "rc80211_minstrel.h"
+
+#define SAMPLE_COLUMNS	10
+#define SAMPLE_TBL(_mi, _idx, _col) \
+		_mi->sample_table[(_idx * SAMPLE_COLUMNS) + _col]
+
+/* convert mac80211 rate index to local array index */
+static inline int
+rix_to_ndx(struct minstrel_sta_info *mi, int rix)
+{
+	int i = rix;
+	for (i = rix; i >= 0; i--)
+		if (mi->r[i].rix == rix)
+			break;
+	WARN_ON(mi->r[i].rix != rix);
+	return i;
+}
+
+static inline bool
+use_low_rate(struct sk_buff *skb)
+{
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	u16 fc;
+
+	fc = le16_to_cpu(hdr->frame_control);
+
+	return ((info->flags & IEEE80211_TX_CTL_NO_ACK) ||
+		(fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA ||
+		is_multicast_ether_addr(hdr->addr1));
+}
+
+
+static void
+minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
+{
+	u32 max_tp = 0, index_max_tp = 0, index_max_tp2 = 0;
+	u32 max_prob = 0, index_max_prob = 0;
+	u32 usecs;
+	u32 p;
+	int i;
+
+	mi->stats_update = jiffies;
+	for (i = 0; i < mi->n_rates; i++) {
+		struct minstrel_rate *mr = &mi->r[i];
+
+		usecs = mr->perfect_tx_time;
+		if (!usecs)
+			usecs = 1000000;
+
+		/* To avoid rounding issues, probabilities scale from 0 (0%)
+		 * to 18000 (100%) */
+		if (mr->attempts) {
+			p = (mr->success * 18000) / mr->attempts;
+			mr->succ_hist += mr->success;
+			mr->att_hist += mr->attempts;
+			mr->cur_prob = p;
+			p = ((p * (100 - mp->ewma_level)) + (mr->probability *
+				mp->ewma_level)) / 100;
+			mr->probability = p;
+			mr->cur_tp = p * (1000000 / usecs);
+		}
+
+		mr->last_success = mr->success;
+		mr->last_attempts = mr->attempts;
+		mr->success = 0;
+		mr->attempts = 0;
+
+		/* Sample less often below the 10% chance of success.
+		 * Sample less often above the 95% chance of success. */
+		if ((mr->probability > 17100) || (mr->probability < 1800)) {
+			mr->adjusted_retry_count = mr->retry_count >> 1;
+			if (mr->adjusted_retry_count > 2)
+				mr->adjusted_retry_count = 2;
+		} else {
+			mr->adjusted_retry_count = mr->retry_count;
+		}
+		if (!mr->adjusted_retry_count)
+			mr->adjusted_retry_count = 2;
+	}
+
+	for (i = 0; i < mi->n_rates; i++) {
+		struct minstrel_rate *mr = &mi->r[i];
+		if (max_tp < mr->cur_tp) {
+			index_max_tp = i;
+			max_tp = mr->cur_tp;
+		}
+		if (max_prob < mr->probability) {
+			index_max_prob = i;
+			max_prob = mr->probability;
+		}
+	}
+
+	max_tp = 0;
+	for (i = 0; i < mi->n_rates; i++) {
+		struct minstrel_rate *mr = &mi->r[i];
+
+		if (i == index_max_tp)
+			continue;
+
+		if (max_tp < mr->cur_tp) {
+			index_max_tp2 = i;
+			max_tp = mr->cur_tp;
+		}
+	}
+	mi->max_tp_rate = index_max_tp;
+	mi->max_tp_rate2 = index_max_tp2;
+	mi->max_prob_rate = index_max_prob;
+}
+
+static void
+minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
+                   struct ieee80211_sta *sta, void *priv_sta,
+		   struct sk_buff *skb)
+{
+	struct minstrel_sta_info *mi = priv_sta;
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_tx_altrate *ar = info->status.retries;
+	struct minstrel_priv *mp = priv;
+	int i, ndx, tries;
+	int success = 0;
+
+	if (!info->status.excessive_retries)
+		success = 1;
+
+	if (!mp->has_mrr || (ar[0].rate_idx < 0)) {
+		ndx = rix_to_ndx(mi, info->tx_rate_idx);
+		tries = info->status.retry_count + 1;
+		mi->r[ndx].success += success;
+		mi->r[ndx].attempts += tries;
+		return;
+	}
+
+	for (i = 0; i < 4; i++) {
+		if (ar[i].rate_idx < 0)
+			break;
+
+		ndx = rix_to_ndx(mi, ar[i].rate_idx);
+		mi->r[ndx].attempts += ar[i].limit + 1;
+
+		if ((i != 3) && (ar[i + 1].rate_idx < 0))
+			mi->r[ndx].success += success;
+	}
+
+	if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
+		mi->sample_count++;
+
+	if (mi->sample_deferred > 0)
+		mi->sample_deferred--;
+}
+
+
+static inline unsigned int
+minstrel_get_retry_count(struct minstrel_rate *mr,
+                         struct ieee80211_tx_info *info)
+{
+	unsigned int retry = mr->adjusted_retry_count;
+
+	if (info->flags & IEEE80211_TX_CTL_USE_RTS_CTS)
+		retry = max(2U, min(mr->retry_count_rtscts, retry));
+	else if (info->flags & IEEE80211_TX_CTL_USE_CTS_PROTECT)
+		retry = max(2U, min(mr->retry_count_cts, retry));
+	return retry;
+}
+
+
+static int
+minstrel_get_next_sample(struct minstrel_sta_info *mi)
+{
+	unsigned int sample_ndx;
+	sample_ndx = SAMPLE_TBL(mi, mi->sample_idx, mi->sample_column);
+	mi->sample_idx++;
+	if (mi->sample_idx > (mi->n_rates - 2)) {
+		mi->sample_idx = 0;
+		mi->sample_column++;
+		if (mi->sample_column >= SAMPLE_COLUMNS)
+			mi->sample_column = 0;
+	}
+	return sample_ndx;
+}
+
+void
+minstrel_get_rate(void *priv, struct ieee80211_supported_band *sband,
+                  struct ieee80211_sta *sta, void *priv_sta,
+                  struct sk_buff *skb, struct rate_selection *sel)
+{
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct minstrel_sta_info *mi = priv_sta;
+	struct minstrel_priv *mp = priv;
+	struct ieee80211_tx_altrate *ar = info->control.retries;
+	unsigned int ndx, sample_ndx = 0;
+	bool mrr;
+	bool sample_slower = false;
+	bool sample = false;
+	int i, delta;
+	int mrr_ndx[3];
+	int sample_rate;
+
+	if (!sta || !mi || use_low_rate(skb)) {
+		sel->rate_idx = rate_lowest_index(sband, sta);
+		return;
+	}
+
+	mrr = mp->has_mrr;
+
+	/* mac80211 does not allow mrr for RTS/CTS */
+	if ((info->flags & IEEE80211_TX_CTL_USE_RTS_CTS) ||
+	    (info->flags & IEEE80211_TX_CTL_USE_CTS_PROTECT))
+		mrr = false;
+
+	if (time_after(jiffies, mi->stats_update + (mp->update_interval *
+			HZ) / 1000))
+		minstrel_update_stats(mp, mi);
+
+	ndx = mi->max_tp_rate;
+
+	if (mrr)
+		sample_rate = mp->lookaround_rate_mrr;
+	else
+		sample_rate = mp->lookaround_rate;
+
+	mi->packet_count++;
+	delta = (mi->packet_count * sample_rate / 100) -
+			(mi->sample_count + mi->sample_deferred / 2);
+
+	/* delta > 0: sampling required */
+	if (delta > 0) {
+		if (mi->packet_count >= 10000) {
+			mi->sample_deferred = 0;
+			mi->sample_count = 0;
+			mi->packet_count = 0;
+		} else if (delta > mi->n_rates * 2) {
+			/* With multi-rate retry, not every planned sample
+			 * attempt actually gets used, due to the way the retry
+			 * chain is set up - [max_tp,sample,prob,lowest] for
+			 * sample_rate < max_tp.
+			 *
+			 * If there's too much sampling backlog and the link
+			 * starts getting worse, minstrel would start bursting
+			 * out lots of sampling frames, which would result
+			 * in a large throughput loss. */
+			mi->sample_count += (delta - mi->n_rates * 2);
+		}
+
+		sample_ndx = minstrel_get_next_sample(mi);
+		sample = true;
+		sample_slower = mrr && (mi->r[sample_ndx].perfect_tx_time >
+			mi->r[ndx].perfect_tx_time);
+
+		if (!sample_slower) {
+			ndx = sample_ndx;
+			mi->sample_count++;
+		} else {
+			/* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
+			 * packets that have the sampling rate deferred to the
+			 * second MRR stage. Increase the sample counter only
+			 * if the deferred sample rate was actually used.
+			 * Use the sample_deferred counter to make sure that
+			 * the sampling is not done in large bursts */
+			info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
+			mi->sample_deferred++;
+		}
+	}
+	sel->rate_idx = mi->r[ndx].rix;
+	info->control.retry_limit = minstrel_get_retry_count(&mi->r[ndx], info);
+
+	if (!mrr) {
+		ar[0].rate_idx = mi->lowest_rix;
+		ar[0].limit = mp->max_retry;
+		ar[1].rate_idx = -1;
+		return;
+	}
+
+	/* MRR setup */
+	if (sample) {
+		if (sample_slower)
+			mrr_ndx[0] = sample_ndx;
+		else
+			mrr_ndx[0] = mi->max_tp_rate;
+	} else {
+		mrr_ndx[0] = mi->max_tp_rate2;
+	}
+	mrr_ndx[1] = mi->max_prob_rate;
+	mrr_ndx[2] = 0;
+	for (i = 0; i < 3; i++) {
+		ar[i].rate_idx = mi->r[mrr_ndx[i]].rix;
+		ar[i].limit = mi->r[mrr_ndx[i]].adjusted_retry_count;
+	}
+}
+
+
+static void
+calc_rate_durations(struct minstrel_sta_info *mi, struct ieee80211_local *local,
+                    struct minstrel_rate *d, struct ieee80211_rate *rate)
+{
+	int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
+
+	d->perfect_tx_time = ieee80211_frame_duration(local, 1200,
+			rate->bitrate, erp, 1);
+	d->ack_time = ieee80211_frame_duration(local, 10,
+			rate->bitrate, erp, 1);
+}
+
+static void
+init_sample_table(struct minstrel_sta_info *mi)
+{
+	unsigned int i, col, new_idx;
+	unsigned int n_srates = mi->n_rates - 1;
+	u8 rnd[8];
+
+	mi->sample_column = 0;
+	mi->sample_idx = 0;
+	memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
+
+	for (col = 0; col < SAMPLE_COLUMNS; col++) {
+		for (i = 0; i < n_srates; i++) {
+			get_random_bytes(rnd, sizeof(rnd));
+			new_idx = (i + rnd[i & 7]) % n_srates;
+
+			while (SAMPLE_TBL(mi, new_idx, col) != 0)
+				new_idx = (new_idx + 1) % n_srates;
+
+			/* Don't sample the slowest rate (i.e. slowest base
+			 * rate). We must presume that the slowest rate works
+			 * fine, or else other management frames will also be
+			 * failing and the link will break */
+			SAMPLE_TBL(mi, new_idx, col) = i + 1;
+		}
+	}
+}
+
+static void
+minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
+               struct ieee80211_sta *sta, void *priv_sta)
+{
+	struct minstrel_sta_info *mi = priv_sta;
+	struct minstrel_priv *mp = priv;
+	struct minstrel_rate *mr_ctl;
+	unsigned int i, n = 0;
+	unsigned int t_slot = 9; /* FIXME: get real slot time */
+
+	mi->lowest_rix = rate_lowest_index(sband, sta);
+	mr_ctl = &mi->r[rix_to_ndx(mi, mi->lowest_rix)];
+	mi->sp_ack_dur = mr_ctl->ack_time;
+
+	for (i = 0; i < sband->n_bitrates; i++) {
+		struct minstrel_rate *mr = &mi->r[n];
+		unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
+		unsigned int tx_time_single;
+		unsigned int cw = mp->cw_min;
+
+		if (!rate_supported(sta, sband->band, i))
+			continue;
+		n++;
+		memset(mr, 0, sizeof(*mr));
+
+		mr->rix = i;
+		mr->bitrate = sband->bitrates[i].bitrate / 5;
+		calc_rate_durations(mi, hw_to_local(mp->hw), mr,
+				&sband->bitrates[i]);
+
+		/* calculate maximum number of retransmissions before
+		 * fallback (based on maximum segment size) */
+		mr->retry_count = 1;
+		mr->retry_count_cts = 1;
+		mr->retry_count_rtscts = 1;
+		tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
+		do {
+			/* add one retransmission */
+			tx_time_single = mr->ack_time + mr->perfect_tx_time;
+
+			/* contention window */
+			tx_time_single += t_slot + min(cw, mp->cw_max);
+			cw = (cw + 1) << 1;
+
+			tx_time += tx_time_single;
+			tx_time_cts += tx_time_single + mi->sp_ack_dur;
+			tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
+			if ((tx_time_cts < mp->segment_size) &&
+				(mr->retry_count_cts < mp->max_retry))
+				mr->retry_count_cts++;
+			if ((tx_time_rtscts < mp->segment_size) &&
+				(mr->retry_count_rtscts < mp->max_retry))
+				mr->retry_count_rtscts++;
+		} while ((tx_time < mp->segment_size) &&
+				(++mr->retry_count < mp->max_retry));
+		mr->adjusted_retry_count = mr->retry_count;
+	}
+
+	for (i = n; i < sband->n_bitrates; i++) {
+		struct minstrel_rate *mr = &mi->r[i];
+		mr->rix = -1;
+	}
+
+	mi->n_rates = n;
+	mi->stats_update = jiffies;
+
+	init_sample_table(mi);
+}
+
+static void *
+minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
+{
+	struct ieee80211_supported_band *sband;
+	struct minstrel_sta_info *mi;
+	struct minstrel_priv *mp = priv;
+	struct ieee80211_hw *hw = mp->hw;
+	int max_rates = 0;
+	int i;
+
+	mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);
+	if (!mi)
+		return NULL;
+
+	for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
+		sband = hw->wiphy->bands[hw->conf.channel->band];
+		if (sband->n_bitrates > max_rates)
+			max_rates = sband->n_bitrates;
+	}
+
+	mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
+	if (!mi->r)
+		goto error;
+
+	mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
+	if (!mi->sample_table)
+		goto error1;
+
+	mi->stats_update = jiffies;
+	return mi;
+
+error1:
+	kfree(mi->r);
+error:
+	kfree(mi);
+	return NULL;
+}
+
+static void
+minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
+{
+	struct minstrel_sta_info *mi = priv_sta;
+
+	kfree(mi->sample_table);
+	kfree(mi->r);
+	kfree(mi);
+}
+
+static void
+minstrel_clear(void *priv)
+{
+}
+
+static void *
+minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
+{
+	struct minstrel_priv *mp;
+
+	mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);
+	if (!mp)
+		return NULL;
+
+	/* contention window settings
+	 * Just an approximation. Using the per-queue values would complicate
+	 * the calculations and is probably unnecessary */
+	mp->cw_min = 15;
+	mp->cw_max = 1023;
+
+	/* number of packets (in %) to use for sampling other rates
+	 * sample less often for non-mrr packets, because the overhead
+	 * is much higher than with mrr */
+	mp->lookaround_rate = 5;
+	mp->lookaround_rate_mrr = 10;
+
+	/* moving average weight for EWMA */
+	mp->ewma_level = 75;
+
+	/* maximum time that the hw is allowed to stay in one MRR segment */
+	mp->segment_size = 6000;
+
+	if (hw->max_altrate_tries > 0)
+		mp->max_retry = hw->max_altrate_tries;
+	else
+		/* safe default, does not necessarily have to match hw properties */
+		mp->max_retry = 7;
+
+	if (hw->max_altrates >= 3)
+		mp->has_mrr = true;
+
+	mp->hw = hw;
+	mp->update_interval = 100;
+
+	return mp;
+}
+
+static void
+minstrel_free(void *priv)
+{
+	kfree(priv);
+}
+
+static struct rate_control_ops mac80211_minstrel = {
+	.name = "minstrel",
+	.tx_status = minstrel_tx_status,
+	.get_rate = minstrel_get_rate,
+	.rate_init = minstrel_rate_init,
+	.clear = minstrel_clear,
+	.alloc = minstrel_alloc,
+	.free = minstrel_free,
+	.alloc_sta = minstrel_alloc_sta,
+	.free_sta = minstrel_free_sta,
+#ifdef CONFIG_MAC80211_DEBUGFS
+	.add_sta_debugfs = minstrel_add_sta_debugfs,
+	.remove_sta_debugfs = minstrel_remove_sta_debugfs,
+#endif
+};
+
+int __init
+rc80211_minstrel_init(void)
+{
+	return ieee80211_rate_control_register(&mac80211_minstrel);
+}
+
+void
+rc80211_minstrel_exit(void)
+{
+	ieee80211_rate_control_unregister(&mac80211_minstrel);
+}
+